The extraordinary garden of Robert Donnelly and Jane Doughty boasts enormous butterfly populations, with hundreds of butterflies counted for Butterfly Conservation Ireland’s National Garden Butterfly Survey annually. On just one day, 27 August 2020, 154 Small Tortoiseshells were counted, feasting on native flowers such as Hemp Agrimony Eupatorium cannabinum. Less frequent garden visitors, such as Cryptic Wood White, Small Copper, Comma, and Silver-washed Fritillary also make Robert and Jane’s garden at Little Eden in County Kilkenny their home.
But Little Eden is not just looking after local butterflies. The garden’s fruit and vegetable yield generated €793.42 from neighbours and passers-by, which Robert and Jane have kindly donated to Butterfly Conservation Ireland. Their help is timely, as we are currently arranging fencing for the front boundary of the reserve in Lullybeg in northwest Kildare to improve the security of the area to ensure grazing livestock needed to conserve the grassland habitats are better contained.
A great thanks to Robert and Jane for all they do for butterflies local and national. The joy of seeing beautiful butterflies in our gardens and beyond, like this Red Admiral, depends on the care for nature shown by Jane, Robert, and all our members and supporters.
Every year, up to this, I have been contacted by one media outlet or another to explain where our butterflies are and why aren’t we seeing them. The interviewer typically prefaces his or her question with, “When I was a child I saw plenty of butterflies, so why am I seeing so few today?”
This year, 2023, is the first year that I was not asked this question. On the contrary, people commented happily about finding large populations adorning gardens and elsewhere this summer (but not in spring) and taking delight at seeing so many. Are they right, or is this just an impression formed by seeing butterflies when people have time off, like during August? Butterfly abundance peaks do not occur at the same time every year, so the poor weather in July is likely to have pushed peaks into August when the weather improved, and people had time to notice.
Let’s leave the butterfly year of 2023 to the annual report we publish under the Report heading. The National Biodiversity Data Centre (NBDC) has published the Irish Butterfly Monitoring Scheme Newsletter for 2022, the warmest year on record. What do the findings tell us?
Firstly, just a quick word on how the information is obtained. The Irish Butterfly Monitoring Scheme (IBMS) involves walking a fixed route (transect) on a weekly basis from 1st April to 30th September each year when weather conditions are favourable. The number of the different butterfly species seen along different sections of each transect are recorded. These records are the basic data upon which the analysis is based. The IBMS tracks population and phenology (time of flight) trends in Irish butterflies, detecting the impacts of factors such as land use and climate change on the Irish butterfly population.
A reduced effort transect scheme, the Five Visit Monitoring Scheme (FVMS) helps to capture abundance. (Several Butterfly Conservation Ireland (BCI) members are involved in these important schemes and BCI runs its own recording scheme which provides data on distribution).
The results in the 2022 report do not make for happy reading.
The multi-species index which estimates the overall direction of change in the butterfly population using Ireland’s most common resident butterflies (15 species) shows that once again there was a moderate decline (-57%) in the number of butterflies flying in 2022 when compared with the baseline year of 2008 (the start of the monitoring scheme). Only the Holly Blue Celastrina argiolus showed an increase in the last 10 years (+149%), with all other species showing uncertain, stable or moderately declining trends.
It is important to note that the multi-species index is a useful index to show overall trends in population changes of common butterflies of the wider countryside. However, it does not generate sufficiently reliable data to track how the populations of our more localised or specialised butterfly species are changing. This is because there is currently not enough data being recorded for these species. To capture adequate information on these species additional species-specific schemes (like the Marsh Fritillary Monitoring Scheme) are needed.
The greatest declines during the period 2008-2022 are the Green-veined White (-81%), followed by Meadow Brown Maniola jurtina (-74%), Ringlet Aphantopus hyperantus (-72%), Large White Pieris brassicae (-71%), and Small Heath Coenonympha pamphilus (-68%). Aside from the Small Heath which has lost the status of being a wider countryside butterfly, all of these are, which suggests that there are significant problems in our environment. These are widespread butterflies, which suggests a widescale environmental crisis. Butterfly abundance will rise and fall naturally from year to year, but these declines span 14 years and are persistent.
Without great changes to farming methods, this is unlikely to change. The causes are not provided by the IBMS data but we can see that our farmed landscape is doused with herbicide, pesticide and synthetic fertilisers. These damage vegetation and butterflies; there is scientific evidence for this, as well as the more subjective, anecdotal support derived from personal experience.
A damp grass field near my home supported common countryside butterflies such as Orange-tip Anthocharis cardamines, Green-veined White Artogeia napi, Cryptic Wood White Leptidea juvernica and the Small Copper. Intensification began to occur. The vegetation was topped early one year to tackle rushes Juncus spp. This did not impact the butterflies but this spring herbicide was applied. It completely removed Common Sorrel Rumex acetosa (Small Copper foodplant), Cuckooflower Cardamines pratensis (Orange-tip and Green-veined White foodplant) and most if not all vetches especially Meadow Vetchling Lathyrus pratensis (Cryptic Wood White). I observed none of these species in this field in 2023. Even when herbicide is not used, nitrates play havoc with many butterflies.
While the EU Nitrates Directive has cut organic nitrates that can be applied to 220kg of nitrate per hectare, this figure is above the safe physiological tolerance level of the larvae of the six butterfly and moth species (Small Copper, Sooty Copper Lycaena tityrus, Speckled Wood Pararge aegeria, Small Heath, Blood Vein Timandra comae and Straw Dot Rivula sericealis) studied by Susanne Kurze and her colleagues.
The Kurze study showed declines in the survival of all six species when fed on sorrels and grass (depending on the moth or butterfly) when their plants were given between 150 and 300 kg N ha−1 year−1. At the higher rate, the sorrels died. The survival rate of the Small Copper was nearly 50% lower in the group fed on N300 than those fed on unfertilised plants. Grass-feeding species also suffered. The survival rate in the Small Heath and Speckled Wood declined by one-third under both nitrogen treatments compared with unfertilised plants. Interestingly, some Speckled Wood larvae survived to pupation but the Small Heath larvae that died did not live longer than 45 days or reach pupation. The most sensitive species was the Straw Dot. Its survival rate declined by half between the control and the N150 treatment and about 80% between the control and the N300 treatment.
This study only scratches the surface. It did not deal with the impacts of these fertiliser concentrations on the overall vegetation in the wild, or the effect of more vigorous plant growth on soil and above-ground temperatures, all of which can also be expected to influence survival rates.
There is a great need for sustainable farming. Stocking rates are absurdly high, maintainable only by massive fertiliser inputs which poison wildlife, pollute water and add to global warming gases.
There is certainly no excuse for continuing to kill off our planet’s most beautiful animals. We waste about one-third of our food, so we are grossly over-producing and over-consuming. Our butterflies don’t need it and nor do we.
Judge, M and Lysaght, L. (2023). The Irish Butterfly Monitoring Scheme Newsletter, Issue 15. National Biodiversity Data Centre.
Kurze, S., Heinken, T. & Fartmann, T. 2018, “Nitrogen enrichment in host plants increases the mortality of common Lepidoptera species”, Oecologia, vol. 188, no. 4, pp. 1227-1237.
After being drenched and underwhelmed by daytime maxima of 13°C during July and August our early September sunshine and warmth is a serious restorative. Today we are looking at 22°C to 26°C; yesterday temperatures climbed above 27°C in some areas; that’s more like it!
Met Eireann tells us that July 2023 was “very wet, cool and dull.” In fact, it was the wettest July on record. The highest temperature recorded in July was on one day, July 7th, and was 24.1 °C in Fanad, County Donegal. While August had better weather, it was not a classic summer month. Described as “mild and changeable” the temperatures were above average nearly everywhere but so was rainfall. Poor Newport in County Mayo had 29 wet days during August!
This doesn’t look like our butterflies should have had a good year, given what our ‘summer’ weather was like, and if I include June this was much better (warmest June on record at most weather stations, with average rainfall). Athenry, County Galway and Shannon Airport, County Clare experienced 27 consecutive days with maximum air temperatures > 20.0 °C, ending on Saturday 24 June. Some of our summer flying butterflies had a spectacular year, with some very high abundance reported to Butterfly Conservation Ireland.
On September 3rd, for example, 246 Small Tortoiseshells were reported from Lullymore, and hundreds of Small Whites and hundreds of Small Tortoiseshells were seen on a wildlife-friendly farm near Maynooth. Red Admirals and Commas are booming too, Green-veined Whites, which love moist, damp habitats, are up, and so are Meadow Brown and Ringlet populations. Holly Blue seems to be thriving and spreading. Early in August, I counted 91 Brimstones just in a small area in Lullybeg; there must have been hundreds of this highly localised butterfly in the bogland in northwest Kildare.
So what can we expect this month? Top of the list is the Small Tortoiseshell, which is everywhere now, even in the Sutton area in Dublin, where the butterfly has gone into a second brood for the first time in many years, thanks probably for July’s bountiful rain and the boost to Stinging Nettles.
The highest numbers of the year are present now but this abundance will be brief. While they are busy feeding, they gain weight and their flight is considerably slower, especially in the cooler temperatures expected as September advances. It is risky to stay on the wing for too long, as dragonflies and birds are eager predators of butterflies. In the past few days, Small Tortoiseshells have entered buildings to look for a secluded nook to pass the winter in. In fact, some will find a spot, retain a topographical memory of its location, and fly out to resume feeding, safe in the knowledge that they know where they will hunker down. Experiments carried out in England show that the Small Tortoiseshell relies on its memory to relocate important sites.
They do not always choose well. A centrally heated building will awaken them in autumn, and deceive the butterfly into the idea that spring is here. Capture and release is not the advised approach; capture and relocation in a cool place is the best policy. A plastic lidded box lined with absorbent kitchen roll in the bottom of the fridge is a good place; no air holes are needed. Release them in March when a warm spell, predicted to last a few days, arrives.
By contrast with the Small Tortoiseshell boom, Peacocks on the wing are few in number. Most are in hibernation and will stay put despite the blandishments of high September temperatures and nectar. This poor Peacock looks the way we might feel after a bad day. Remarkably, this butterfly flew away, albeit awkwardly, after the photo was taken. Staying out late is risky, as pointed out earlier!
Another butterfly that passes the winter in the adult stage, the Brimstone, is similarly out there in greatly reduced abundance. Most of them are concealed in evergreen foliage, blending with their leaflike wings to aid blending. We will see a few still feeding, and these are wisely very close to over-wintering cover.
Green-veined White butterflies really suffer from droughts, but not this year. Here is a male on Devil’s-bit Scabious, his forewings packed with citral (C10H16O), a pheromone used to seduce a female. It is a powerful, sweet fragrance, easily detected by a human, so it must be an all-enveloping experience for a female Green-veined White. This butterfly is still breeding and the species will pass the winter as a caterpillar.
And now for something different! The next two butterflies are migrants. Unlike our resident butterflies, these two are not cold-adapted species. Unlike our resident natives, these do not have a rest phase in their life cycle and are continuously brooded, which means they breed and grow throughout the year. In more technical language, they do not undergo a diapause phase. If a butterfly cannot delay breeding, it requires the correct conditions to reproduce throughout the year. These conditions are not currently available in most of northern Europe, so an escape strategy must be applied. Migration is a way to avoid the onset of unsuitable conditions. In spring and summer, the heat in North Africa and parts of Southern Europe drives some migrants north to find the conditions needed.
The Red Admiral is our most regular migrant butterfly. It occurs in Ireland from about March to November and they leave during the autumn months. When the herbaceous flowers are gone, it uses ivy nectar, sap runs and overripe fruit for sustenance. There are still Red Admiral larvae on nettles so we will see the adults for some weeks yet.
The lovely Clouded Yellow is a visitor too, but in smaller numbers and often later in the year, especially during September and October. In some years a mass arrival followed by breeding occurs. In these years, they arrive earlier, usually from April onward.
In years when they arrive later, the Clouded Yellow does attempt to breed, but it is likely that the attempts fail as the temperatures drop. But the butterfly is a delight to see whenever it appears. This female was seen in Lullymore by Pat Wyse and Fionnuala Parnell, enjoy!
Back to our resident butterflies, the Comma is beginning to hatch its second generation which flies during autumn. This makes it unique among our butterflies. We will say more about the Comma in our October post, but keep a close eye on ripe blackberries and ivy in the coming weeks.
The heatwave during the first week in September has coaxed migrants from southern Europe to journey north. This Vestal is one of four to visit a garden in County Meath on 7th September. The colour of this moth is strongly influenced by the temperature experienced by the pupa with bright specimens like this one the result of hotter conditions, suggesting that this one is from the Mediterranean area of Europe or North Africa. It is mainly a nocturnal moth but can be found on grass stalks during the day.
All photos by J. Harding except Clouded Yellow P. Wyse.
There is a drop in the number of moth species present in the garden in August compared with June and July but there is still variety in my moth trap, with some intriguing species. Here is a selection of moths that fly during August.
The Magpie is a striking moth that flies at night but occasionally during the day too. I recently watched a female flying on a sunny afternoon, laying eggs on Berberis thunbergii atropurpurea, a purple-leaved garden plant used for hedging or as an individual specimen. It breeds on a wide range of native plants Common Hazel, Common Hawthorn, Common Spindle, Heather (in Scotland and presumably here). It is capable of long flights, and famously Orkney and Shetland were colonized by it in the last few years. It appears to enjoy good abundance in Ireland but it has declined in England and Wales.
The Chinese Character might be better called the Bird Dropping moth for its resemblance to a bird dropping. This breeder on Crab Apple, Common Blackthorn, Common Hawthorn, Rowan, and other trees appears to be avoided by birds. Certainly, my Robin, who loves seeing my moth trap light up, shows no interest in this enigmatic moth. This moth is double-brooded.
The Scalloped Oak is also nocturnal and while it breeds on oak, it uses a wide range of trees as well as Honeysuckle, Bilberry and Heather. Given such a wide range of foodplants, it occurs in a range of habitats, such as woodland, hedges, gardens, parks, and bogs. It has one generation every year.
The Gold Spot is double-brooded, nocturnal, and occasionally day-flying when the day is muggy and overcast. It likes wet habitats, as it breeds on sedges, Yellow Iris, Branched Bur-reed and Water-plantain. It occurs in gardens that hold ponds with marsh and marginal vegetation.
The Pebble Prominent is generally common, breeds on willows and is double-brooded. In some years I get only one or two, but this year has been better, with five found last Wednesday.
The Bee moth is a very interesting micro-moth that breeds on the nests of a range of wasp and bee species. Their yellow caterpillars protect themselves from their hosts by spinning a tough silk case, while they feed on the comb, honey, stored food, and even meconium (fecal matter). They can destroy nests and are considered a pest by beekeepers. Both sexes use sex pheromones during courtship and males sing to females by vibrating their abdominal plates. A courtship dance by both sexes occurs before mating. While this appears to be a destructive species, it should be noted that all species have their enemies, and it is rarely if ever the case that one species destroys its host, under circumstances of a functional ecosystem.
The Canary-shouldered Thorn is very well-named! It breeds on Downy and Silver Birch, Alder, limes, elms, Goat Willow, and Hornbeam. It is strictly nocturnal and flies in just one generation a year, from July to mid-October. It spends the daylight within trees, concealed on the underside of leaves.
As you can see, these moths breed mostly on native plants or, in the case of the Bee Moth feed on hosts that use native plants. By making native trees, shrubs, and flowers the key architecture of your garden, you will be making homes for our native moths and all the species that depend on moths for their survival. The Russian revolutionary Lenin is quoted as having said, “Everything is connected to everything else.” Without the elements needed, our ecosystems would collapse. Moths are excellent indicators of ecosystem functioning because they play such key roles mainly by providing food, pollination, and plant growth regulation. We have c. 1567 moth species in Ireland, so they are a significant proportion of our invertebrate population. Together with butterflies, the order Lepidoptera makes up about 9% of all life forms on the planet. We cannot do without them.
Just one pleasure that you as a nature lover can enjoy is simply strolling through your favourite haunt and seeing what’s there. Like me, you might not recognise every creature encountered but the identification challenge adds a layer of interest and purpose to your ramble. The pleasure of exploration and discovery might prompt further inquiry, more learning, and a greater understanding of the complexity of our wonderful world. In this post, I will show you some of the photos I took on a recent ramble, explain a little about each species, and try to give an impression, however superficial, of how these characters fit together in their world, and ours, and how this can change over time.
First up is a Comma butterfly. Intriguingly, this butterfly exists in two forms. You can tell something about the life the caterpillar led by looking at the adult. If when the caterpillar when developing, it was feeding on nettles with a high nitrogen content, and receiving 18 or more hours of sunlight, or was developing when daylight hours were increasing, it is likely that a light-form adult would emerge in July/August. This light-coloured Comma breeds soon after emerging. If the day length was marginal, and the larva fed on nutritious leaves in warm conditions, a light Comma is also likelier.
A dark Comma results when the caterpillar fed when the day length was declining, or it was cool and the plant was not especially nutritious. The dark Comma will rarely breed until the following spring. It behaves like the Peacock butterfly that hatches in summer, feeds, and enters hibernation in cool, dark, dry situations in woodland. A much darker underside makes it far harder for birds to find than light-coloured Commas.
Then I sighted a female Brimstone, resting. Like the Peacocks, which were found nearby, it was not very active and was not looking to fly into the path of a male. Neither of these two will mate until next year. Both pass the winter as adult butterflies. The brimstone among leaves that match its outline and vein markings, the Peacock in dark places that match its black underside.
A large wasp-like creature busily foraging on a Wild Angelica flower caught my eye next. This is an ichneumon wasp, one of many similar-looking wasp species. These wasps make a living from moth caterpillars and other insect groups and arachnids (spiders) by parasitising them. The noctuid moth family is often used as hosts for these wasps, which inject eggs into the caterpillars, or lay near them, develop inside the caterpillar before emerging from the dead or dying caterpillar and pupating. Ghoulish though it sounds, the wasps regulate population sizes and, indirectly, vegetation growth, preventing mass population booms that threaten to self-annihilate by eating all their food.
Another wasp-like creature was on the Wild Angelica, but this one is not a wasp, but a fly. The Two-banded Wasp Hoverfly is well-named. A nectar-feeder as an adult, the larva feeds on aphids. It is quite a striking-looking creature but is usually seen singly.
A much quieter creature next took my eye. This was a Tortoise Shield Bug, a plant feeder. Another one was on bramble, the Green Shield Bug, another plant eater. If disturbed it often emits a marzipan smell, which is quite cloying, but harmless. If cutting your meadow back in late summer or autumn you might notice it! It spends the winter as an adult and breeds the following spring.
The pondside scrub vegetation yielded two male Beautiful Demoiselles, which were displaying, hoping to catch a girl’s eye. They were skittish, landing only briefly so I was delighted to get a photograph. It needs fast-flowing, clean, pebble-or sandy-bottomed streams. The pond is fed by a clean stream, with a marl bottom, which obviously keeps it happy.
The skittishness of males might be related to their need to protect an egg-laying site from other males. His female must lay her eggs there under his protective gaze. If not, an interloper might mate with ‘his’ female and replace his sperm. It is a tough life being a male Beautiful Demoiselle!
A sighting that surprised me was a male Holly Blue. It is a less frequent butterfly in rural locations, preferring suburban and urban gardens where there are heat traps, and masses of holly and ivy for breeding. The butterfly uses many other plants for breeding, but these are the main choices, in spring and summer/autumn respectively. The one I saw was feeding on Common Heather, slate blue among pink evoking delicate beauty.
Another surprise is the number of very fresh Meadow Browns. This species emergence times are quite uneven across the country, even with an individual county. Thus, 29 Kilometres away on the Kildare/Meath border, the Meadow Brown is now scarce, with a few faded, geriatric specimens flapping weakly in sheltered places. In Lullybeg it remains abundant, with several newly hatched individuals like the one pictured seen on my early August ramble.
When I arrived home, I checked some roadside Stinging Nettles. Under a large leaf about halfway down the stem of a nettle was a Comma caterpillar, in its second instar. This caterpillar is developing under rapidly declining daylight, meaning that it is guaranteed to be a dark Comma. This will, should it survive, be flying in September, and will join its uncle, pictured at the start of this article, in hibernation. Therefore, our spring Comma population, all (or nearly all?) dark form Comma butterflies, consists of two generations from the previous year, ones that hatched from their pupae in July/August and the second brood adults hatching in September/October.
The ramble showed how interactions are taking place between different aspects of the biodiversity encountered. The wasp, hoverfly and butterflies fed from flowers, pollinating them to produce seeds for plant reproduction and seed-eating animals. The butterfly larvae eat plants and are in turn eaten by parasites and other predators, which themselves are used in the food web. Species regulate and are regulated by other members of their community. This creates a balance, so no member of the community dominates at the expense of others, over time.
There are deeper interactions than can be described here, but one interesting study that might indicate the effects of climate warming on some of our butterflies and their community has been conducted in Sweden. The Swedish study looked at four nettle-feeding butterflies and at how climate change has influenced their populations, in the context of the arrival of the nettle-feeding Map Butterfly, which is tracking climate change by extending its European range northward, just like the nettle-feeding Comma.
The study, Rewiring of interactions in a changing environment: nettle-feeding butterflies and their parasitoids (citation below) looked at the interactions between four nettle-feeding butterflies and their shared parasitoids in Sweden and the impact of the newly arrived Map butterfly, via its parasitoids, on three long-term residents, the Small Tortoiseshell, Peacock and Red Admiral (the Red Admiral is described by the study as a resident, but it is a migrant to Sweden, breeding there annually).
They collected 6777 wild larvae of the four species over two years. Of the 6777 collected larvae, 1508 were parasitised (22%) and produced parasitoids from three families: Tachinidae (Diptera), Ichneumonidae (Hymenoptera) and Braconidae (Hymenoptera). They identified 11 species: the tachinids (flies) Pelatachina tibialis, Sturmia bella, Phryxe vulgaris, Phryxe nemea, Pales pavida and Blondelia nigripes, the ichneumonids (wasps) Phobocampe confusa, Thyrateles haereticus and Thyrateles camelinus, and the braconids (wasps) Microgaster subcompleta and Cotesia vanessae. Some of these parasitoids have not been recorded here; those that occur in Ireland are in bold. Overall, 76.7% of the parasitised larvae were parasitised by either Pelatachinatibialis (34.6%), Phobocampe confusa (28.5%) or Sturmia bella (13.6%). All four butterflies were attacked by these three parasitoids, except for the Map butterfly which was not infected by P. confusa. The Red Admiral was attacked by most parasitoid species, including representatives of all three families. Unknown causes were also responsible for caterpillar mortality.
The most heavily parasitised butterfly was the Small Tortoiseshell, followed by the Peacock. The Red Admiral was third and the Map butterfly was least impacted. Parasitism rate increased in the Peacock when its larvae were found with the larvae of the Map butterfly and Red Admiral but decreased when it co-occurred with the Small Tortoiseshell. For its part, parasitism increased in the Small Tortoiseshell when its larvae occurred with those of the Peacock. They also observed that the parasitism rate in the Peacock increased with the number of co-occurring butterfly species. Looking at parasites that infect both the Map and the native butterflies (Peacock, Small Tortoiseshell and Red Admiral) they found that Small Tortoiseshell had higher levels of infection when it co-occurred with the Map.
It was also discovered that in the Swedish sites where the Map was known for the longest, the Small Tortoiseshell and Peacock had higher rates of parasitism. The low rates of parasitism in the Map and Red Admiral are discussed but no definite conclusion is made. However, one strong possibility for the low infection rate in the Map is that because the Map is a recent colonist in Sweden, it may have escaped its parasitoids initially, and is only beginning to recruit parasitoids in the last c.10 years. In areas where the Map had only recently arrived, infection rates were lower for the Small Tortoiseshell and Peacock.
The Map might be causing higher infection rates by shared parasitoids by providing a host for the parasitoids when the larvae of the Small Tortoiseshell and Peacock are scarce. The three species’ caterpillars overlap in their occurrence, but there are phenological differences (differences in the timing of the appearance of the caterpillars).
Populations of the Small Tortoiseshell are bivoltine (two generations) in Sweden. Its larvae are recorded from early May to the end of August with the first generation being found from early May and the second generation from late June. The Peacock is univoltine (one generation) in Sweden with larvae observed from late May to early August (like in Ireland). The Map is a bivoltine species but in contrast to the Peacock and Small Tortoiseshell, which overwinter as adults, the Map hibernates in the pupal stage. Larvae from the first generation are found in the field in June; larvae from the second generation are found from the end of July to early September. The Red Admiral is a migratory butterfly in Sweden and its population depends on the migratory influx from the areas where the species is resident. It is univoltine in Sweden with larvae observed in the field from May to early September.
All species are distributed across Sweden, except for the Map which is currently limited to the southern half of the country.
Therefore, there are times in the year when Map larvae are plentiful but those of the Peacock and Small Tortoiseshell are less numerous. Phenological differences in the parasitoids between hosts might also mean the Map is assisting increased infection rates in its butterfly relatives. If correct, the Map is reducing the competition for its food (nettles) during its establishment phase, but if the Map recruits more parasitoids, as the study indicates is likely, a balance between the four butterflies might be struck.
However, the Swedish study did not look at several other potentially relevant factors, including the parasitoids that the Map may have introduced to the other three butterflies, only looking at shared parasitoids, and looked at larval parasitoids, not egg or pupal ones. Thus, a warming climate that causes a butterfly to extend its range may bring challenges for established natives. We simply do not know the extent of these. The study does not point out that all four of the nettle-feeding butterflies occur further south in Europe.
While I love the Comma butterfly and rejoice in its colonising zeal, are our established natives being put under increased survival pressure? In Ireland, the Comma has been found breeding mainly on the Stinging Nettle. The recent decline in the Peacock population in northwest Kildare coincides with the establishment of the Comma in the area, but this abundance decline might be coincidental and related to many other factors, such as weather conditions, changes in the habitat, unshared parasitoids, changes in the behaviour and population of the parasitoids, viruses, and bacterial infections unrelated to the Comma’s arrival.
None of this is known. But it certainly adds intrigue.
Our Small Tortoiseshell, Peacock, and Red Admiral populations are very important in our landscape because they are common, widespread, and often abundant. The impact on the wider community is all the greater if they decline because these abundant animals connect with a large range of species.
That happy, carefree ramble reminds us that we have so much to learn. Keep watching our butterflies, our canary in the coal mine.
Audusseau, H., Ryrholm, N., Stefanescu, C., Tharel, S., Jansson, C., Champeaux, L., Shaw, M.R., Raper, C., Lewis, O.T., Janz, N. & Schmucki, R. 2021, “Rewiring of interactions in a changing environment: nettle‐feeding butterflies and their parasitoids”, Oikos, vol. 130, no. 4, pp. 624-636.
August is a great butterfly month, but listening to the rain splattering above my head as I write I should probably append the adverb ‘allegedly’. The weather forecast for the first week in August is for dull, wet and at times windy weather, not the right conditions for flying insects. Our butterflies are accustomed to our wet, erratic weather, and even brief sunshine is capitalized on, with often impressive abundance as butterflies have emerged from pupae and are waiting to fly.
An impression of abundance is often noted on the first sunny day following days of rain, with exciting numbers evident. This population boom should not be confused with an increasing trend. Typically, butterfly pupae hatch over weeks, but if the weather is unfavourable, several days’ hatched butterflies will wait to fly together on the first good weather day, rather than fly in apparently reduced abundance over several days with good weather conditions. Similarly, pupae that have been ready to hatch for some days may delay hatching until a sunny day arrives.
Assuming the sun shines in our wet and wild countryside, what can we expect to see?
This depends not just on the habitat but where in Ireland it is you are looking for butterflies. The Meadow Brown, on its ‘last legs’ in many areas in the east, is just beginning to emerge in abundance in many areas of the west and northwest during August.
Huge abundance can be encountered on coastal grasslands in Donegal and Clare during August, fresh and eager to mate, while their eastern cousins are faded or dead. By contrast, the Small Copper can be seen in suitable habitats throughout Ireland during August.
A butterfly with a restricted Irish distribution that flew in spring should be around in August. The Wood White, a Burren and western limestone butterfly will be flying in its habitats. This second flight is a partial generation. The first flight, which occurs mainly during spring comprises all the over-wintered pupae.
The last Irish butterfly to emerge is the Brown Hairstreak. Our largest and rarest hairstreak exists in the Burren (Clare and Galway) and a small number of areas outside the Burren, such as west Tipperary, Ennis, near Lee’s Road, around Lough Corrib, Lough Mask (both Galway) and possibly Lough Carra (Mayo). This obscure but beautiful species is associated with wilder, bushy places typically (but not always) on exposed carboniferous limestone. It peaks in abundance during August and has been seen as late as October. Look out for it on bramble flowers, and on Creeping Thistle near scrub.
Another butterfly that is restricted in its Irish distribution but more widely distributed than the Wood White and Brown Hairstreak is the Brimstone. The new generation flies from July to September or even early October but its peak flight is in August. The Brimstone joins the Peacock and Small Tortoiseshell to gorge on nectar in flower-rich areas close to woodland before all three species go into hibernation. Bramble, Common Knapweed, Rough Hawkbit and Devil’s-bit Scabious are favoured flowers for all three.
A lovely, small (19-20 mm wingspan) intensely coloured day-flying moth to look for on wild grassland is the Small Purple-barred. Ranked ‘Near Threatened’ on our Macro-moth Red List 2016. This moth breeds on Common Milkwort, which need semi-natural grassland untainted by agricultural chemicals. A common day-flying moth during August is the Shaded Broad-bar, a brown/buff grassland moth with a dark brown crosswise bar on its forewings.
On limestone grassland, chiefly in the Burren, the Straw Belle may be encountered; it is a nocturnal species that is easily roused in daylight. Straw-coloured and brown-freckled with a brown diagonal bar on the forewing, this species is especially common on short Burren grassland. A moth confined to the Burren, the Burren Green, ranked ‘Near Threatened’ is abundant in the Burren during August. This moth is mainly nocturnal, but it will fly in daylight on muggy, over-cast days when it feeds on Common Knapweed. This moth is not found outside the Burren in Britain and Ireland. It breeds on Blue Moor-grass.
These are just a few of our August flyers. We will leave you to discover others, but remember to let us know what you see, according to the record submission procedures here:
Butterfly Conservation Ireland’s reserve at Lullybeg is monitored using the transect system. This uses a fixed route to count butterflies on the reserve between April 1st and September 30th each year. The count includes all butterflies seen 2.5 metres to the left and right of the walker, 5 metres ahead of the walker and 5 metres above. The results of these counts are sent to the National Biodiversity Data Centre. In addition, counts are made on the reserve away from the transect.
Having systematic butterfly count data for the site since 2011 means trends in species and abundance can be tracked which means we can check the effects of changes in management, successional changes in the habitats, weather conditions and even climate on butterfly populations.
Here we give an indication of the reserve’s performance at the halfway stage in 2023.
The reserve has some species whose conservation is a concern nationally, and these are especially important monitoring subjects. The Small Heath, rated Near Threatened, has dramatically declined on the reserve. From a high of 231 individual Small Heaths in 2013, a slight drop to 229 in 2014, the trend has been of steady falls since. The years 2015, 2016, 2017, 2018, 2019, 2020, 2021 and 2022 saw 131, 62, 61, 63, 57, 44, 74 and 35 Small Heaths respectively.
This year the Small Heath count is 54, a healthy increase on 2022’s poor result but still much lower than its peak in 2013 and 2014. We are investigating the habitat conditions it likes on the reserve to inform decisions about how to manage these areas and how these conditions compatibly align with the ecological requirements of other important butterflies. This is quite a challenge in a relatively small reserve.
One conclusion is that the Small Heath dislikes heavy grazing. This is clear from the nearby reserve at Lullymore, where it has been eliminated by grazing designed to cater for the Marsh Fritillary, where donkeys were introduced to graze on Purple Moor-grass to prevent it from overwhelming the Marsh Fritillary foodplant. The Small Heath likes fescue grasses, and the growth form it especially likes is tall, shaggy, dense tussocks containing plenty of dead grass blades. Unfortunately, grazing livestock love this grass, and attack this before tackling the rougher species.
The Small Heath also likes smaller, sparser Red Fescue growing among sparsely vegetated ground, but semi-bare terrain is quite temporary on vegetated cutover peatlands. Thus, successional change is a threat, unless the fescues grow into dense tussocks needed, but this only happens if grazing does not occur or is very sporadic. The ground can be disturbed by cattle to create bare patches, but will Red Fescue colonise these quickly before more robust grasses assume control?
The timing of grazing and topping of vegetation and the severity of topping are also important. Late autumn or early winter grazing and topping is probably best for the butterfly. These were used in 2022 and a population rebound was observed, but some of this recovery was in areas not grazed and not topped.
A priority butterfly that is doing well on the reserve is the Marsh Fritillary. A mere 15 were counted in 2011, followed by 19 in 2012, 41 in 2013, 92 in 2014, just 32 in 2015, 14 in 2016, 17 in 2017, 31 in 2018. After this numbers increased.
Totals of 287 and 207 in 2021 and 2022 respectively show this recovery. This spring and summer 246 Marsh Fritillaries were counted, great news that shows the management is working well for this threatened species. The control of scrub and light grazing is key to this success.
Another threatened butterfly, the Dark Green Fritillary is still on the wing, so the picture is unclear at this point. Only two males have been recorded so far. There are plenty of Common Dog-violet plants in parts of the reserve but the sward around the highest violet populations is probably too low for this species.
The Silver-washed Fritillary has shown lower numbers in recent years. In 2020, 2021 and 2022 the figures were 9, 6 and 8 respectively. Up to mid-July 2023, 16 Silver-washed Fritillaries have been seen and this number will increase, so that is very good news.
So far in 2023, 1237 Ringlets have been counted (only 636 in 2022), and 168 Meadow Browns (204 in 2022). These two are still flying, so the totals will rise.
Twenty-two Dingy Skippers were found this year; its flight period is over for 2023. In the four years 2019-2022, the numbers seen were 10, 10, 47 and 31. The trend will be closely monitored next spring.
It is wonderful to see increases in the Small Heath, Marsh Fritillary, Silver-washed Fritillary and Ringlet, and an expected rise in Meadow Brown numbers. Without your help, none of this would happen.
These figures show what is possible elsewhere in our countryside if managed properly. Land managers and conservationists take note!
At last month’s Bloom event in the Phoenix Park, Dublin, a question asked in the Irish Wildlife Trust (IWT) tent about the installation of industrial infrastructure on bogs was answered by the IWT’s Patrick Fogarty. He described the bleak condition of Ireland’s bogs and made it clear that plantation forestry, wind farms, solar farms, dumps, and roads should not be located on the nation’s bogs, which should be restored to allow them to recover from decades of mining and drainage.
Responding, a lady from the audience stated that as a Dublin resident who does her best to be green, she felt very depressed about the detailed description of the extent of the degradation of our bogs and other peatlands and habitats generally.
She does her best. She has a compost heap, plants flowers for pollinators, recycles her recyclable waste and probably uses public transport whenever possible and may use an electric vehicle for destinations that are not served by public transport. She does not burn fossil fuels; she has solar panels and has retrofitted her walls and roof space with insulation. She might also have had double-glazing units fitted and wears extra layers of clothing to minimize the amount of electricity used during the colder months.
She might be buying clothing made from organic cotton and eschewing ‘fast fashion.’ If she is a mother, she might use cloth or biodegradable nappies.
Surely, she pleaded, she was doing enough. What else is she to do?
As a society, we don’t know how diminished our environment is.
Let us probe a bit deeper.
She has a compost heap. Why does she need a compost heap? According to the Environmental Protection Agency Irish households threw away an estimated 241,000 tonnes of food (31% of the total) in 2020. Excessive purchase creates an impetus to over-produce and encourages the practices of intensive farming that removes habitats and poisons our atmosphere, water, and soils. Shoppers need to think more about food quantity. Do we need to buy so much food? Consumer behaviour feeds back into food production practices, so choose less, and pay more for sustainably produced food.
If you don’t overbuy food, you will not generate the same amount of packaging waste either.
She plants flowers for pollinators. That sounds great, but it often makes matters worse.
Where did the plant come from, what species is it, how much fertilizer was used to produce it and what is the growing medium?
The plant is most likely an import from Europe. It was not grown from native seed or native cuttings. It travelled here by boat or aircraft and by delivery vehicle, adding to transport emissions.
Regarding species, it might be a plant native to another part of the world. Plants sourced from other ecosystems often cause ecological damage when placed in our habitats and are often of very limited value to Ireland’s wildlife. A gardener’s favourite is Buddleia davidii and cultivated varieties of this plant. This plant is often called the Butterfly Bush. It attracts butterflies but it does not attract many species and its leaves feed very few moth larvae and no butterfly larvae.
Despite its blooms being festooned with glorious Peacock, Red Admiral and Small Tortoiseshell butterflies especially, it is very limited in its overall value to pollinators. A recent study Conserving Diversity in Irish plant-pollinator Networks (2022) concerning plant-pollinator relationships compiles a top 33 plant list. Buddleia is not on it.
Even worse is the choice of another flowering shrub, Fuschia.
This plant has escaped into the wild and is wreaking havoc on natural habitats, displacing native, insect-rich shrubs. Again, it attracts bees but its leaves feed very few native insects. Our native shrubs do have central roles in our ecosystems, sheltering and feeding the immature and adult stages of our insects. But these are ignored by many gardeners who think that buying visually appealing non-indigenous plants marketed ‘Bee Friendly’ or with a Peacock butterfly pictured on the label means their choice is nature friendly.
This is slick marketing, not ecological truth.
Further strain on our world is evident in the plastic pot, the synthetic fertilizer and peat used in the growing medium the plant comes in. All these items require energy to produce, with oil also a component in the plastic pot and fertilizer. The production of these two materials adds to the atmospheric pollution driving climate change and habitat damage on a global scale. The peat was robbed from the environment. Robbed, not ‘harvested.’ This impoverished or completely removed the peatland habitat leading to the extinction of the Curlew from most of its Irish range with more extinctions to follow. Peat removal pollutes streams, rivers and lakes and atmosphere.
While I lack the data to prove this, there is a possibility that attracting butterflies by planting Buddleia damages the butterflies that benefit from the rich nectar provided.
Buddleias planted in sunny, sheltered situations will attract butterflies, sometimes in impressive abundance. It appears to be doing so much good. Day after day of Large Whites, Red Admirals, Peacocks, Small Tortoiseshell, Commas, and even Silver-washed Fritillaries. What’s not to like?
Concentrating butterflies in a small area concentrates predators too. I frequently observe small birds such as Robins, Blue Tits and Wrens being drawn to Buddleias to attack butterflies. Both birds prefer to hunt in shrubs, so the presence of the butterflies on this bush makes them more vulnerable to avian attack. Furthermore, concentrating birds in a small area may make contagious diseases a greater threat. Buddleia is a bird table for butterflies, and insectivorous birds, but it may turn out that both groups end up sacrificed on the altar of our good intentions.
The answer is to grow our native herbs and native trees widely. Garden centres grow according to demand. Much better, harvest native seeds from wild places nearest to your home and create compatible habitats in gardens and green spaces. By ‘compatible’ I mean the natural habitats that are represented locally and that belong together. If you farm, farm with nature. Get advice from your farm advisor about the best ways to do this.
Electric vehicles are not a panacea for Greenhouse gas (GHG) emissions from the transport sector. We still generate power by burning fossil fuels so powering up electric vehicles contributes to emissions. Unless we get our power from clean energy sources that do not involve habitat destruction we are doing no real good. Even when clean, renewable energy is produced sustainably, the construction process for EVs is very severe on the environment with some dreadful consequences in many areas mined for the materials used for the EV batteries.
Insulating one’s home, and installing double-glazed windows and solar panels will help to reduce energy consumption and lower GHG emissions. Where you can, get rid of hard surfaces such as tarmac, brick drives and concrete. New builds should use as much natural material as possible. Natural slate (not always expensive, depending on the source), clay roof tiles, natural stone and clay brick should replace concrete, the production of which requires enormous energy and generates massive CO2 emissions.
But to take this article back to where it began, we must re-wet our bogs and other wetlands, re-plant native woods and allow existing native woods to expand, reduce the pressure on land by producing and consuming less, grow food with reduced or no chemical inputs and generally allow nature to return. The crisis must be tackled at every level, in one’s home, garden, neighbourhood, nationally, and globally.
The soaring temperatures across southern Europe and the United States and flooding and drought elsewhere are alarms we must not ignore. Those who rejected the EU Nature Restoration Law should consult their conscience and intelligence.
The signs of the warming climate are evident in a range of climate statistics. In this article, we look at the most recent data and explore the effects the changes are having on our butterflies, moths, and the places they need for survival.
The world’s average temperature reached a new high on Monday 3 July, topping 17 degrees Celsius for the first time.
And according to Met Eireann, June 2023 was the hottest June on record in Ireland, breaking an 83-year-old temperature record. The increasing temperature is not a one-off, but a trend towards a warmer climate. Met Éireann climatologist Paul Moore states:
An average monthly temperature of greater than 16C has been seen in July and August but never before in June. June 2023 was well above normal due to persistent warm days and nights.
Further afield, Spain experienced extreme heat as early as April when temperatures exceeded 38 Celsius. According to the World Meteorological Organization, Europe is warming twice as fast as other continents and Ireland is feeling the effect.
According to Met Éireann’s TRANSLATE report, Ireland’s climate has shown changes in temperature and rainfall. Daily annual average precipitation has risen between the two baseline periods, 1961-2010 and 1991-2020. Ireland is wetter, with the western half of the country showing the biggest increases. Temperatures have risen throughout the country with the highest temperatures recorded in the centre of Ireland.
The report also deals with climate projections:
As the world warms it is clear that Ireland’s temperature and rainfall undergo more and more significant changes, for example on average Summer temperature could increase by more than 2°C, Summer rainfall could decrease by 9% while Winter rainfall could increase by 24%.
Butterflies can tell us a great deal about how climate is affecting our environment. Butterflies and moths respond quickly to changes in the environment because they are highly sensitive to temperature, precipitation and habitat change. Their rapid reproduction rate means that populations can rise very quickly when favourable conditions prevail but abundance crashes when conditions are less suitable.
Abundance is not the only response butterflies show to a warming climate. Distribution changes, earlier emergence, extended and shorter flight periods, changes to brood structure, and even appearance can occur in butterflies.
An extreme weather (EWE) is an event that is rare at a particular place and time of year. Extreme weather events, such as extreme heat, extreme drought and extreme rainfall are expected to be more common, and these will have an impact. I will look at extreme weather events first.
Extreme Weather Events
Met Éireann’s TRANSLATE report states that as the climate warms, extremes become more widespread and pronounced. A study by McDermott Long et al. (2017) looked at the impact of extreme climate effects on all life stages and the over-wintering period of UK butterflies. This study showed that the pupae of several single-brooded species (univoltine) are vulnerable to prolonged precipitation. This study also found that extreme heat during the period starting on November 1st and ending on February 28th has a negative impact on the population of the over-wintering stage of single-brooded species (whether this is the egg, larva, pupa or adult).
However, extreme heat during the adult life stage outside winter causes positive population change for 21% of species and extreme heat during the pupal stage outside winter is also positive, while during over-wintering it is associated with negative population change in 45% of species. The study discovered that extreme cold during the adult life stage of single-brooded butterflies has a negative effect on 35% of species.
The study looked at the impact of extreme climate effects on butterflies that produce two or more broods (multivoltine) annually. It found that extreme heat during over-wintering and extreme precipitation during the first and second generation adult life stages are the biggest cause of population declines in multivoltine species (67%, 58% and 50% of all multivoltine species affected, respectively). Extreme heat during the adult life stage is associated with positive population change in 42% of species. Drought plays a much more important role in multivoltine species than in univoltine species. Drought negatively affects 50% of species during their second larval life stage but has a positive impact on 25% of the species during their first ovum life stage.
In summary, butterfly population changes are primarily driven by temperature extremes. Extreme heat is harmful during over-wintering periods and beneficial during adult periods (outside winter) and extreme cold had opposite impacts on both life stages. Harmful effects were identified for extreme precipitation during the pupal life stage for univoltine species.
One species that has undergone a range change is the Comma butterfly. In fact, it had not been recorded in Ireland before 1998.
In The Irish Butterfly Book (2021), I explored the role of climate change in its colonisation of Ireland since 2000, a process that has accelerated since 2014:
Asher et al. (2001) and Thomas and Lewington (2014) state that climatic factors appear to be relevant, particularly climate warming. The factors driving the recent expansion of range into Ireland are likely to be a warming climate and closeness to an expanding British population. Unlike the gregarious larvae of the Small Tortoiseshell and the Peacock, which bask communally to heat up, solitary Comma larvae are not able to raise their own body temperature above that of their surroundings. This dependence upon external temperature might explain the absence of the Comma from Ireland in the past when the climate was cooler.
The Comma usually breeds on Stinging Nettles, on mainly unshaded plants, especially using plants growing in damp soils near trees and shrubs, where the Comma benefits from warmth, shelter and succulent foodplants. In May 2023 I confirmed its use of elm in Ireland, probably Wych Elm Ulmus glabra, as a foodplant for the caterpillar. The Wych Elm and Stinging Nettle are the optimal foodplant choices for successful larval development (Braschler and Hill 2007).
We have gained other species, and species already here that had a limited range here are extending their Irish range. Moths such as Blair’s Shoulder-knot (first recorded in 2002) and the White Satin moth are colonists extending their range, while moths like the Yellow-tail and Marbled White-spot, formerly quite restricted in Ireland are in expansion mode. The Bedstraw Hawkmoth might be colonising Ireland, with adults and larvae being recorded in various places across the country. Lime Hawkmoth is another recent arrival, appearing now to be well-established in parts of Dublin, breeding on lime trees on tree-lined roads.
One way of tracking the response of living things to climate events is the study of phenology. Phenology is the study of periodic events in biological life cycles and how these are influenced by seasonal and interannual variations in climate, as well as habitat factors.
In Ireland, the Orange-tip, largely a spring butterfly, usually starts to fly shortly after the end of the first week in April until the end of June. Sometimes an early July sighting is made. The peak flight time is in the first half of May. It has one brood in Ireland and throughout its vast European range. It is likely that some of the pupae over-winter twice, a strategy to cope with prolonged inclement conditions during their flight period.
The trend in Britain, where records of butterfly phenology are more extensive than in Ireland, is toward earlier emergence. Here I look at just one example of earlier emergence trends. Throughout most of the twentieth century, the first British Orange-tip of the season was recorded, with very few exceptions, in April.
But since 1989, most of the earliest emergences have been in March (Oates 2015). The average first sighting date 2011-2021 for the Orange-tip in Britain, compiled by Butterfly Conservation UK, is March 17th.This indicates the impact of warmer springs. The average first sighting date 2013-2017 for the Orange-tip in Ireland, compiled by Butterfly Conservation Ireland, is later, on April 10th, reflecting the cooler temperatures here. However, the mild spring of 2019 saw an Orange-tip recorded on March 29th, in County Donegal, while in 2021 the first Orange-tip was recorded, again in Donegal, on April 3rd.
The Orange-tip, like several other butterfly species, passes the winter in the pupa, so it is well placed to emerge earlier when spring has sustained warmth.
Earlier adult emergence dates are being recorded for several species such as the Marsh Fritillary, Large Heath, Narrow-bordered Bee Hawkmoth and others.
But earlier life cycle events are not limited to adult emergence dates. The hatching dates of larvae might also be taking place earlier than was recorded in the past. On June 29th 2023, I found two Marsh Fritillary nests containing newly hatched caterpillars in Lullybeg, in County Kildare. Judging from the leaves they consumed, hatching occurred a few days before June 29th. This hatching date is up to one month earlier than recorded in this area in the past.
Extended and shorter flight periods and abundance
The effect of increased warmth is already being expressed in the lives of our moths and butterflies.
The Red Admiral, a migrant, typically arrives in Ireland in March and departs during autumn. In some places, like Howth, County Dublin, it is remaining during winter, taking advantage of the warmer winters to breed on nettles that now survive because winter frosts rarely occur there now.
Sustained summer warmth and dryness do not suit all species. The Small Blue breeds on just one foodplant that grows on thin soils, such as sandy soils. The plant, Kidney Vetch, can shrivel during drought, which means the larvae will starve or be under-sized. Droughts have already stricken the species, such as when the prolonged drought in 2018 was followed by a population crash on the sand dunes at Portrane, County Dublin, in 2019, and presumably elsewhere.
Changes to Brood Structure
Brood structure refers to how many generations an animal can produce per year. In Ireland, most butterfly species produce one generation a year. Some can produce two or even three generations, while some species, such as the Red Admiral, are continuously brooded.
The Small Copper, typically a bivoltine butterfly in Ireland, appears to benefit from sustained warm weather. This butterfly can fly in three generations in Ireland in years with warm summers, and in two broods when the summer is cooler. We have seen third broods in recent years, such as in 2021 when the recorded flight period was May 7th to October 9th. It appears that only two generations flew in 2020 when summer was cooler and the recorded flight period was May 8th to September 6th.
A species that might be vulnerable to increasing warmth and decreasing summer rainfall is the Small Tortoiseshell.
The Small Tortoiseshell can fly in two or even three generations, but the second might be a partial generation while any third brood will be very small. Adult Small Tortoiseshells can usually be found flying from March-May (over-wintered adults), June-July (first brood) and late August-early October (second brood, small third brood). All final brood Small Tortoiseshell butterflies enter hibernation, often in houses.
An interesting phenomenon has been recorded in a Small Tortoiseshell hibernaculum in St Albans, Hertfordshire, where the butterfly went into early hibernation in some years (Hull, 2019). In 2017 and 2018, all the Small Tortoiseshells that hibernated in Malcolm Hull’s unheated shed were hibernating by July 7th and August 5th, respectively. In 2016, the last five did not enter hibernation until mid-October. In 2017 and 2018, the butterfly had effectively abandoned the second generation and entered reproductive diapause. The weather during June and July 2018 was hot and dry and the Stinging Nettles needed for breeding may have become unsuitable.
Frank Smyth, a very experienced observer has noted the absence of Small Tortoiseshells at Howth, County Dublin during August and September in some years but their reappearance the following spring. The butterfly may be skipping its second generation at Howth too, and this may occur in other dry east coast locations during dry summers. A skipped second generation might also occur during cold summers. This ability to modify its brood strategy suggests a level of adaptability, much needed by a widely distributed species in an era of climate change.
Changes in appearance
Butterflies, moths and other insects, such as dragonflies, show morphological responses to climate and weather conditions. Thus, some butterflies produce smaller offspring during or following drought. Common Blue butterflies that emerge in summer following drought are often greatly reduced in size. This is the result of a reduction in the quality and or the amount of edible foodplant. In years with good rainfall and warmth, adults are larger.
The Dark Green Fritillary (to take one example) present in Ireland, Scotland and other cool climates are darker than their counterparts in sunnier, warmer climates, an adaptation to overcast, cool conditions. As our climate becomes sunnier and warmer, it is likely that our darker Dark Green Fritillaries will become paler.
A Climate Warming Success
One butterfly that has successfully tracked climate change is the Comma. This butterfly is a fascinating example of a butterfly whose development and brood structure are adapted to daylight length. Increasing hours of daylight see eggs laid in late April and early May producing direct breeding adults that breed soon after they emerge from their pupae in June and July. These are paler, well designed for bright sunshine. Eggs laid later in spring produce mainly dark adults which postpone reproduction until the following spring. Even more intriguing is the ability of the caterpillar to switch to producing the adult form best adapted to the conditions. Swedish research found this is influenced by two main factors: the length of daylight experienced by developing caterpillars and whether days become shorter or longer as they grow (Nylin, 1989).
I suspect the Comma’s development might also be accelerated by increasing night warmth. It is known that caterpillars can develop into the direct breeding form even when day-length is declining if the temperature is warm, and they are feeding on very nutritious food (Thomas and Lewington, 2014). In captive breeding indoors during spring, I observed Comma larvae feeding at night, in darkness, likely benefiting from indoor warmth. Despite darker conditions indoors, all the larvae I reared in spring produced pale, direct-breeding adults. The adults hatched shortly before and around 18 June 2014. Warming night temperatures may increase the percentage of direct-breeding Commas hatching in June and July, even when day length is declining after the summer solstice (June 21st).
Furthermore, warmer daytime spring weather arising from climate change will likely result in more direct-breeding adults for two reasons: earlier adult emergence and faster development of eggs and larvae. Over-wintering adults emerge earlier if spring weather is warm and sunny, and breeding may occur earlier, followed by earlier egg-laying on earlier developing nettles, earlier hatching and faster development of larvae under warmer conditions, meaning that more larvae will be developing when daylight is still increasing.
The direct-breeding adult Commas (light form) that hatch from pupae in June and July reproduce and die weeks before August ends. Their offspring develop mainly during July, August and September, when day length is declining, and nettles are less lush than they were in spring. The resulting adults are dark and these delay breeding until spring after hibernation. However, Nylin (1989) states that some exceptions occur with some dark male adults breeding in summer (under laboratory conditions) and some pale adults over-wintering (Eeles, 2019). (Nylin also found that only dark (normal form) adults are produced in the wild in Sweden.)
Braschler and Hill (2007) investigated the Comma’s expansion and point out that polyphagy (the ability to use several foodplant species) may enhance the ability of species to track climate change although the females sometimes chose suboptimal foodplants (Gamberale-Stille et al. 2014). There are species (such as the Small Blue, Small Tortoiseshell and Marsh Fritillary) that use just one foodplant, leaving them vulnerable to changes that negatively affect their food. Prolonged summer drought will affect many moisture-dependent species, such as the Ringlet and Green-veined White. No longer will these be the abundant, widespread species we know today.
There is evidence that climate change is challenging efforts to protect rare and endangered butterflies. Climate change and nitrogen deposition, or a combination of the two, are considered likely candidates for driving habitat change leading to longer growing seasons and increased grassiness on the Morecambe Bay limestones in northwest England, leading to 50% less food (violets) and a cooler micro-climate for the warmth-loving larva of the High Brown Fritillary (Ellis et al. 2019). This effect may be occurring in the Burren, impacting our very rare Pearl-bordered Fritillary butterfly.
The future picture of our environment under the range of potential climate change scenarios is not clear. Predictions at the level needed to anticipate the ecological impacts on butterflies and moths may not be possible. The most immediate answer is to protect the habitats we have and restore what can be restored. Large-scale habitats with the best conservation management and the fullest range of conditions that apply to habitats are the best safeguards against our changing climate.
Much of the information in this article is from The Irish Butterfly Book by Jesmond Harding. For more information about the way climate and related factors are hitting our butterflies, read The Irish Butterfly Book. Contact the author by email: email@example.com
BBC, 2023. Climate change: World’s hottest day since records began. Available at https://www.bbc.com/news/science-environment-66104822 accessed 05 July 2023
Braschler, B. & Hill, J.K. 2007, “Role of larval host plants in the climate-driven range expansion of the butterfly Polygonia c-album”. The Journal of animal ecology, vol. 76, no. 3, pp. 415-423.
Butterfly Conservation UK , 2023. First Sightings 2021 and previous. Online at https://butterfly-conservation.org/butterflies/first-butterfly-sightings-2023/first-sightings-2021-previous accessed 03 July 2023.
Eeles, P. (2019) Life Cycles of British & Irish Butterflies. Pisces Publications, Berkshire.
Ellis, S., Wainwright, D., Dennis, E.B., Bourn, N.A.D., Bulman, C.R., Hobson, R., Jones, R., Middlebrook, I., Plackett, J., Smith, R.G., Wain, M. & Warren, M.S. 2019, “Are habitat changes driving the decline of the UK’s most threatened butterfly: the High Brown Fritillary Argynnis adippe (Lepidoptera: Nymphalidae)?”, Journal of insect conservation, vol. 23, no. 2, pp. 351-367.
Gamberale-Stille, G., Söderlind, L., Janz, N. & Nylin, S. 2014, “Host plant choice in the comma butterfly-larval choosiness may ameliorate effects of indiscriminate oviposition: Host plant choice in the comma butterfly”, Insect science, vol. 21, no. 4, pp. 499-506.
Harding, J. (2021) The Irish Butterfly Book. Privately Published, Maynooth.
Hull, M (2019). Where have all the Small Tortoiseshell gone? (online) https://hertsmiddx-butterflies.org.uk/SmallTortoiseshells.pdf (Accessed 04 April 2020).
McDermott Long, O. An investigation into the vulnerability of UK butterflies to extreme climatic events associated with increasing climate change. Doctoral thesis, University of East Anglia, 2017.
Nylin, S. (1989). “Effects of changing photoperiods in the life cycle regulation of the comma butterfly, Polygonia c-album (Nymphalidae)”. Ecological Entomology, 14(2), 209–218. doi:10.1111/j.1365-2311.1989.tb00771.x
Oates, M. (2015) In Pursuit of Butterflies. Bloomsbury, New York.
Based on four key climatic indicators, temperature, sunshine, rainfall and wind speed, the favourability index for butterflies is highest in June, July and August. More species fly in July than any other month. Thirty-one species are in flight in July, with some species having their abundance peak in July. The Comma first generation, the Silver-washed and Dark Green Fritillaries, Essex and Small Skipper hit their numerical heights in July.
Here we profile a selection of July flyers.
A large, colourful and magnificent butterfly, its flight is powerful and elegant. Whether in level or climbing flight, the Silver-washed Fritillary scores highly on pace and agility. The courtship flight is utterly unforgettable, a picture of synchronised romance, a complex ritual that has captivated generations of butterfly lovers. The female flies in a level flight, as if totally oblivious to the male, who loops repeatedly under her, then up in front of her. Woodland rides and clearing are the venues for this dance, while pairing follows in a tree, shrub, on Bracken, and occasionally on the ground.
Where to find the Silver-washed Fritillary
Open woodland, with violets plentiful in clearings and in the interior of the wood. Knocksink Wood, Enniskerry, County Wicklow, the woods around Lough Leane in Killarney, County Kerry, the oak woods at Crom in Fermanagh, Ravenwood in Wexford, the Furry Glen in the Phoenix Park, Dublin and woods with native trees and sunlit woodland floors containing violets, its larval food, throughout the country.
A striking butterfly, known by its underside hindwing comma marking, is perhaps the most interesting mid-summer species. Why?
It hatches in two forms, a dark form, which has an upperside ground colour of orange-red, and a light form, a golden coloured Comma named the hutchinsoni form (the hutchinsoni form, shown above, also has an underside that is lighter in colour) after Emma Hutchinson who bred the species in Herefordshire, one of its last British strongholds in the late nineteenth century. Unbelievably given its abundance in Britain today, and its increasing presence in many areas in eastern Ireland south of Louth and into the Irish midlands and beyond, it was believed to be on the brink of extinction in Britain in the 1880s, for reasons unknown. It was unknown in Ireland until 1998.
Emma Hutchinson bred vast numbers of Commas and sent them to areas of England it disappeared from. One such county is Surrey but despite a large release, the Comma did not repopulate the county.
A feature Emma Hutchinson noted is the butterfly’s ability to adapt to weather conditions by producing two forms; the golden form is produced following springs and early summers with warm weather and the darker form arises when conditions are cloudy, dull, and cool. The dark-form Commas don’t breed in the year of their birth, but feed briefly and hibernate. The golden Commas breed on emergence, taking advantage of fine summer weather. All offspring of the golden Commas are dark, fly in autumn and pass the winter as adult butterflies. Good spring and summer weather produces more golden Commas and two generations. Cold summers lead to fewer golden Commas, more dark Commas, and a small second generation. This account of the adaptable breeding strategy is more complex than stated here but this general outline holds good for most of our Commas.
The Comma breeds on Stinging Nettles and larvae have recently (May 2023) been recorded on elm.
Where to find the Comma
Still scarce or absent from most of Ireland, the Comma is still expanding its Irish range following its establishment in the southeast early this century. It is common in woods in Counties Carlow, Wicklow, Wexford, Kildare and Dublin, where it is found in wooded areas such as open woodland, hedged lanes, tree-lines along rivers and other waterways, mature wooded gardens throughout these counties. Elsewhere, it is becoming more numerous although it is still not abundant. In the last few years, it has reached Counties Limerick, Clare and Down and this westwards and northwards march is expected to continue. It is most evident in March-May, July and September and October.
Dark Green Fritillary
If this butterfly was a Premier League footballer, it would be a tricky, pacy winger, dashing towards goal, showing dramatic and unexpected changes of direction while at other times being more direct but always dynamic. A large, hyperactive and dazzlingly fast butterfly, it is a stunning sight when freshly emerged. The males will battle strong winds on cliffs and hills, eye-catchers who swoop and dive, passing in and out of view. The male is a deep, shining orange marked with black ticks, dots and chevrons. The female is more sedentary, darker, and highly variable. Typically, she is a duller orange with enlarged dark markings. Underside hindwings are green with spangled with reflective silver.
Where to find the Dark Green Fritillary
This butterfly likes flower-rich locations. The Burren, in Counties Clare and Galway, Sheskinmore in County Donegal, and Ballyteigue Burrow on the south County Wexford coast are among its key locations in Ireland. Coastal areas, especially vegetated sand dunes are also good places to look for it. This butterfly is highly vulnerable to agricultural intensification. Flower-filled grasslands lose their value for this butterfly when fertiliser or slurry is applied. It needs unspoiled grasslands rich in violets, its breeding plant, for its survival.
This butterfly usually has two generations a year. Found in the areas of contiguous exposed carboniferous limestone from south of the Burren northwards close to the southern border of County Mayo, this small unspotted white is notable for its low, floppy flight, a soporific sight on a hot, sticky day in late July. Breeding on vetches growing among scrub on hot dry limestone habitats, it is one of our rarer butterflies and should be monitored. The first flight is usually in May and the second flight is in mid/late July to mid-August.
Just one interesting feature is that the female appears to have poor botanical skills. She frequently tests the wrong plants before eventually finding the correct larval foodplant on which to lay an egg. She searches in the right places but often alights on plants that are not even related to vetches. She’s not alone in her confusion. Her relative, the single-brooded Cryptic Wood White (which usually flies from May-early July), which looks identical, does the same!
The main foodplants observed being used in Ireland are Meadow Vetchling, Tufted Vetch, and Bitter Vetch.
Where do find the Wood White
The Burren area where open scrub on limestone pavement contains vetches and other flowers is its stronghold in Ireland but it has been confirmed on western limestones elsewhere such as around Ennis further south in County Clare and in limestone habitats around Lough Corrib, such as west of Lough Corrib at M 19532 40634, in the Carrowmoreknock area. It might also occur at Lough Carra, County Mayo.
Unless a dedicated search of oak woodland, usually with binoculars, is made, you are very unlikely to see this small but beautiful creature. Both sexes have silver undersides but the darker undersides are tinted violet in the male and purple in his mate. Here we show both sexes to illustrate the differences. The butterfly is known for occupying positions often very high up on oaks and for being very active during the evenings. They are also known to be nocturnal, although I don’t know the extent of their activity after dark. I have seen it fly in almost complete darkness and it is attracted to light traps set for moths.
The oak woods in Phoenix Park, Dublin, Tomies Wood, Killarney, County Kerry, and oak woods in Wicklow such as Glendalough and Glen of the Downs are good places to look for them. Scan the canopy for the butterfly during sunny weather, especially after 5 pm. It’s about the size of the Common Blue butterfly.
Enjoy watching butterflies this summer, and be sure to let us know about your butterfly records. You can find out how to send us your observations under the Records tab on this website.