Let it Bee

The snow and ice is still melting, and spring is attempting to make itself felt.  Warmth, when it comes, will awaken our insects, our bees, moths and butterflies. Their first priority i to find food; after all, many of our insects have fasted for six months and need to recover diminished body weight to build reserves for activity, such as flight, mate-seeking and breeding.

One of the great challenges faced by nectar and pollen dependent insects is a simple but critical one of a lack of food. If the grassy hedge-bank in which a bumblebee hibernated is  cut severely, the Primroses, Cowslips and Common Dandelions on it will be killed or be so reduced that flowering does not take place as it should. Worse still, some flowery verges, hedge banks and lawns are sprayed to kill ‘weeds’. A bland green desert replaces colour, and the endless Saturday drone of lawn mowers and the snarl of strimmers replaces the hum of bees shouldering their way through the leafy vegetation..

Happily, there is action being undertaken and lots we can do ourselves.

The National Biodiversity Data Centre has, since 2015, been involved in the National Pollinator Plan which describes actions that can be undertaken by me and you, by public bodies such as county councils and community groups, such as Tidy Towns to enhance the landscape for our flower feeders. Please click on this link and take on at least one action suggested.:


If you are encouraged by rising daylight to pop to the local garden centre to brighten up the garden, look for plants that are good for insects. Not all very attractive flowers are valuable. Some are almost useless. Begonias, many roses, gladioli, daffodils contain little or no pollen or nectar. As far as helping bees and butterflies is concerned, these plants might as well be plastic ornaments.

Here are some suggestions. Herbs such as mint, Wild Marjoram, often called oregano, borage and thyme carry lots of nectar. Lavenders are good too. Primrose, by which I mean the native Primula vulgaris will be welcome, as will the native Irish Cowslip, Primula veris.  Hebes, small to medium-sized evergreen shrubs produce lots of nectar too, and when planted in warmer coastal areas, these plants bloom in winter, and sustain insects that wake up on mild days. There is even evidence that the hebes grown by gardeners on Howth Head is helping Red Admiral butterflies, which usually leave our shores in autumn for sunny climes further south to remain there throughout the winter.

For mid-summer, there are buddleias which are medium-sized shrubs that like sunny, dry conditions. Bees and butterflies are irresistibly drawn to these shrubs, and you will have weeks of pleasure observing their antics. Verbena bonariensis, a tall, willowy flower that bears purple flowers is a great draw too, and this will provide nectar into September. Ice Plant, a small succulent plant, flowers in September and if in a sunny sheltered spot, be ready for crowds of bees and butterflies.

Personally, I prefer the native Irish flowers. Willow flowers in spring are a big favourite for bees, moths and butterflies. I already mentioned Cowslips and Primroses, but the Common Dandelion trumps these. I cannot think of any butterfly that rejects this plant, and when the seeds are ready, Goldfinches will be fed. Common Hawthorn blossom in May is a lovely sight and also a great nectar source. Wild roses, like Dog-rose, Rosa canina, is good too. Honeysuckle is terrific for bees and moths, and its fragrance on a June night is an essential summer scent. Two final winners; Common Knapweed, Centurea nigra and Devil’s-bit Scabious Succisa pratensis will between them, feed our bees, butterflies and moths from June to October.

A couple of further tips. Do not mow your lawn too tight and cut it every six weeks from April to October to allow Red Clover, Common Bird’s-foot-trefoil to fatten our insects. These flowers bring crimson and gold to your lawn too, cheering the place up! And to go all the way, sow a wild flower meadow consisting of these flowers, along with Common Knapweed and Devil’s-bit Scabious and leave uncut from May to September, depending on the warmth of the season-delay mowing/strimming longer in cool years. Cut on a high setting. Remove cuttings to keep the  soil suitable to grow your wild flowers the following year.

Never use sprays.

Relax, and enjoy sharing your garden with nature. By taking the steps described here and in the video, you will be enhancing the survival chances of our flowering plants, insects and broader biodiversity as well as increasing the value of your home and garden for your own well-being. People’s well-being is improved by contact with high levels of biodiversity. Make your garden a haven for you, your loved ones, and the creatures who would share it with us, if we gave them what they need.

Enjoy spring!

All photos ©J.Harding.

Clouded Yellow butterfly which feeds and breeds on Red Clover.
Red Admiral on Buddleia davidii.
Devil’s-bit Scabious, flowers from August to October.
Shrill Carder Bee on Common Knapweed. This bee is now rare, confined to the best remaining flower-rich habitats.
Ashy Miner Bee on Common Dandelion. This solitary bee nests in bare soil banks.




Butterfly Impacts from Extreme Climatic Events (ECEs)

An earlier post looked at the effect of extreme climatic events on butterflies but this topic is timely given the current heavy snow.

A study published in 2017, Sensitivity of UK butterflies to local climatic extremes: which life stages are most at risk? examined the impact of ECEs on the resident UK butterfly species (n = 41) over a 37-year period. The study investigated the sensitivity of butterflies to four extremes (drought, extreme precipitation, extreme heat and extreme cold), identified at the site level, across each species’ life stages. Variations in the vulnerability of butterflies at the site level were also compared based on three life-history traits (voltinism, (how many broods a species will produce in a year), habitat requirement and range.

This is the first study to examine the effects of ECEs at the site level across all life stages of a butterfly, identifying sensitive life stages and unravelling the role life-history traits play in species sensitivity to ECEs.

Butterfly population changes were found to be primarily driven by temperature extremes. Extreme heat was detrimental during overwintering periods and beneficial during adult periods and extreme cold had opposite impacts on both of these life stages. Previously undocumented detrimental effects were identified for extreme precipitation during the pupal life stage for univoltine species. Generalists (widely distributed butterflies that use a range of habitats, such as the Small White) were found to have significantly more negative associations with ECEs than specialists (local species confined to  specific habitats, such as the Small Blue).

With future projections of warmer, wetter winters and more severe weather events, UK (and probably Irish) butterflies could come under severe pressure given the findings of this study.

What does this mean for our butterflies given the cold winter and heavy snow?

Extreme cold in winter has a beneficial effect on butterflies but cold weather during adult flight period in spring and summer is very negative. Extreme heat in winter, expressed as very mild weather in Ireland when we are likely to see Small Tortoiseshells on the wing during January, is very negative. Certainly, the butterfly will be on the wing at a time when its adult food and larval food is unavailable. Paul Waring in his excellent Field Guide to the Moths of Great Britain states that the large decline in the Garden Tiger moth population may be due to mild, wet Januarys followed by colder weather in February. The Garden Tiger overwinters as a larva which may become active during mild January conditions when food-plant quality may be poor. Feeding requires heat for digestion, and sudden onset of cold weather may affect the animal’s digestive processes and damage the food-plant leaving it vulnerable to starvation. The report also considered that extreme warmth in winter made larvae more susceptible to disease and fungal infections, but the report believes that causing the species, whether over-wintering as an adult or larva to become active before the food is available is a more likely cause of decline.

It is interesting that habitat specialists are at less risk (but are still negatively affected) from extreme climatic events. Factors that may contribute to this reduced impact may be protection given to them by their habitats, the fact that all but one (the Wood White) of our habitat specialists are single-brooded. Indeed, the report found that drought had a much more negative impact on multi-brooded species than on single-brooded species. Yet this does not apply to all life-stages; drought during the egg-stage was noted as a driver of population increase. Furthermore, the response to drought across the species studied was not as uniform as the response to the other extremes. However, there is no doubt that ECEs affect specialists; extreme cold in May and flooding arising from unseasonably heavy rain has eliminated Marsh Fritillary colonies.

Interestingly, the report, when considering why ECEs have a greater effect on generalists than specialists makes the hypothesis that generalist species are more vulnerable as they are filling their climatic niche, and hence, many populations within the species range may be situated on the climatic range edge and be more vulnerable to increased climate inconsistency outside of their comfort zone. In contrast, specialist species are confined to particular host plants which may not common across the specialist species’ climatic niche; hence, those specialist species are not filling their climatic niche and are effectively in or close to their core range and are not subjected to ECEs that are outside their ability to adapt and cope. It is also possible that specialist species are being protected by their habitats where they have been able to survive.

Finally, the report, while careful not to be too definitive, concludes with some important findings. Butterflies (especially single-brooded species) could benefit from warmer, drier summers associated with climate change but milder, wetter winters would damage populations. A key finding is to make sure that habitats do not become fragmented, especially for specialists, and that habitat management should look to protect species from extreme warmth in winter-not a problem for us in 2018!

Peacock on snow. This was disturbed from a wooded area and was returned to over-wintering. ©J.Harding.
Down which road does the future of our butterflies lie? ©J.Harding.

Reserve Management Event Report

Today we had a sunny, dry and mild day at last, giving perfect conditions for tackling scrub at Lullybeg. We further broadened the track connected the excellent habitats at Lullymore and Lullybeg by cutting back scrub on both sides of the track.

This intervention has a number of benefits. The track itself contains excellent habitat. It contains a high density of the nectar-rich perennial, Devil’s-bit Scabious, which is fed on by adult butterflies in July, August, September and October. This plant is the only larval food plant of two important species of lepidoptera, the Narrow-bordered Bee Hawkmoth and the Marsh Fritillary butterfly. Increasing the levels of sunlight entering the track has allowed the Marsh Fritillary to move in to breed. We found two larval nests last autumn, and re-found these today. The nests are large, and the larvae were basking in today’s sharp late winter sunshine. Direct sunlight is vital to the larval development, and conditions created here by clearing work carried out in 2017 and continued today has yielded positive results.

The habitat here approximates to the Annex I habitat under the 1992 Habitats’ Directive, Molinia grassland (grassland rich in Purple Moor-grass). This grass dies back to a straw colour and this is vital for the Marsh Fritillary larvae, and other species’ larvae which use it as a basking site. Another larva to do this is the Ruby Tiger moth larva, which over-winters as a fully-fed caterpillar but which needs to bask for several weeks before pupating in April. This leaf litter is also used by Brimstone butterflies as basking sites in spring. Furthermore, the track contains two species of small tree, Purging Buckthorn and Alder Buckthorn, used by the Brimstone butterfly for breeding. This butterfly lays on unshaded plants, and prefers plants that are both unshaded and sheltered, making the plants growing here ideal for this beautiful and local butterfly.

The shelter and the removal of shading scrub creates a warm micro-climate which draws in many insects, making the area a very attractive site for dragonflies to feed and to heat up. The scrub bordering the track creates a warm, especially sheltered woodland edge habitat, a natural patrolling edge for male butterflies engaged in mate-seeking. This is especially evident in the case of Orange-tips and Brimstones in spring, and Silver-washed Fritillaries in mid-summer.

Finally, the track connects the rich grassland habitats in the wider area, allowing for connectivity and dispersal within the landscape. Evidence for the use of the track for dispersal has been observed in the Marsh Fritillary, a mainly sedentary butterfly which occasionally moves to colonise new habitat patches and maintain genetic variety by mating with individuals from other existing populations. Marsh Fritillary butterflies have been seen entering the track, from both Lullymore and Lullybeg, suggesting a connection and interaction between the two populations. Research strongly supports the need for populations of this species to remain connected by dispersal, and barriers such as a block of woodland may be sufficient to isolate colonies, which has often proved to be very damaging to the long-term survival of this vulnerable butterfly.

Later in the year we will get to observe the benefits of our work, for butterflies are quick to exploit new opportunities, making for a satisfyingly quick return on our investment!

Thanks are due to all who support our work in any way, and particularly to our members who put in such great work today.

Ruby Tiger larva basking, Lullybeg.©J.Harding.
Marsh Fritillary larvae basking on Purple Moor-grass blades, Lullybeg.©J.Harding.


What February means for Butterflies and Butterfly-lovers.

The following article by Jesmond Harding appeared in The Irish Times on February 3rd 2018. The brief was to say what February means for  seekers of butterflies in 150 words.

February is a winter month, and the year’s coldest, says Met Éireann. For butterfly-lovers, February continues the butterfly famine. Butterflies that over-winter as adults remain concealed in woodland, muted underwings blending with greys and browns of tree trunks or mimicking holly, bramble and ivy leaves, in the case of the Brimstone butterfly.

Spring is coming even if it seems a distant hope. The poet Edward Thomas suggested that, in February, spring must be dreamed up. To ideate spring the butterfly-lover seeks the white golf-ball eggs of the Brown Hairstreak butterfly on dark leafless Common Blackthorn stems and nests of spiky hedgehog-like caterpillars of the Marsh Fritillary, huddling together in lucid February sun.

Occasionally, a warm day rouses a Peacock, Small Tortoiseshell, Comma or Brimstone butterfly. These bask on walls, tree trunks and tufts of dry grass litter, but soon return to their winter abodes. They’re not out of the woods yet.

Brimstone takes shelter under a bramble leaf at Lullybeg, County Kildare during bright but cool weather in early April, 2013.©J.Harding.


Annual Report 2017

Butterfly Conservation Ireland Annual Report 2017 is now available under the Report tab.

We thank everyone who helped to produce the report and we hope you find it interesting.

Marsh Fritillary, Kildare. Photo copyright J.Harding

How to Care for Hibernating Butterflies

In Ireland we have four butterfly species that over-winter in the adult form.  We have a number of moths that hibernate as adults. One of these is the iconic Herald moth. A group of this species will sometimes shelter in your attic to wait for spring.

One of our butterflies has a habit of entering rooms in houses to pass the winter. The Small Tortoiseshell, a beautifully marked butterfly likes to stay close to us in late summer and will even stake out likely hibernation sites indoors during August and September before settling to fold its wings for winter in some obscure spot in our homes, sheds or even cars! This well-studied butterfly has some fascinating characteristics. It has shown an ability to relocate specific sites when it has been disturbed from the site, suggesting a spatial memory; if a nettle on which a female is laying her eggs is moved, the female returns to the spot where the nettle was located, not to the site it was removed to. The butterfly is very mobile and some of our butterflies are likely to fly here from Britain and Europe. Males establish and defend territories but if he finds a female he switches to defending the female from other males. She makes him work hard, with the male often having to fight several males throughout the rest of the day. He will drive them away by engaging in a series of aerial combats, with high altitude climbs when he tries to fly above the intruder. When the intruder is expelled, the male returns to his female who usually remains perched where he left her. Sometimes, though, she gives him the slip, giving him an anxious search as he inspects the surrounding nettle bed for her. Some females hide, and later accept defence by another male. Even a female which has cooperated with a male all day tries to lose him when she goes to roost in the nettles in the evening by dropping into the nettles and running along the ground. If the male manages to stay with her, she suddenly becomes quiet and allows mating, which lasts all night. Presumably her demanding behaviour ensures that only the fittest males father offspring, ensuring the health of the next generation. This provides a fascinating example of selection by the female of the fittest male.

Another, related feature of the butterfly is its impressive longevity. The over-wintering generation is long-lived, and individuals can survive 10 months. The impressive life-span allows the female Small Tortoiseshell the chance to be selective; most female butterflies accept the first male encountered; these females lack the luxury of an extended life to test male powers of endurance.

However, our Small Tortoiseshells have one significant challenge when they enter our homes to see out the winter in our bedrooms, living rooms and hallways. The butterflies are very careful to select the best spots, picking excellent hiding places in curtain folds, behind mirrors and pictures, in unused chimney brests, behind dressers and, to complete the concealment, their dark cryptic coloured undersides blend nicely with their chosen surface. However, the mod con that is central heating confounds their attempts to complete their winter slumber. Heat rouses the butterfly, causing it to believe that spring, with its sunshine, flowers and nettles beckon it to fly outdoors. The confused butterfly flies around lights and windows, trying to get out.

Householders who release the butterfly into the winter are usually dooming it. The butterfly rapidly loses the ability to fly when its body temperature plummets in the cold and is picked off by birds or mammals. The other problem is starvation. The butterfly built up vital fats by gorging on nectar in our gardens and countryside before switching off for winter and long periods of unseasonable activity reduces these reserves.

What should you do if you encounter an active Small Tortoiseshell in your home?

If this happens in warm spring weather release the butterfly in the knowledge that it’s time to let it go. It is now ready to feed on the spring flowers, move in search of territories, breeding grounds and mates.

If the butterfly wakes up in winter it should be placed in a dry, transparent container lined with a folded section of kitchen roll to absorb moisture and placed in the salad drawer in the fridge, where the temperature is around four Celsius. The butterfly will soon settle and can be kept there until warm, sunny weather arrives in March or April.  Alternatively, remove the butterfly from the container when it is quiet and place in an unheated shed or room to complete its winter rest.

If the butterfly has been flying around for some time, it may need to be fed. Dissolve sugar or honey in hot water, allow it to cool and use a cotton pad to absorb the sweetened solution. When cool, place the calmed butterfly (cooled in the salad drawer but not long enough to be made fully docile) on the pad, in softly-lit mild conditions. It should begin to feed. When it has finished, place in a cool place to sleep.

Over the years I have successfully over-wintered adult Small Tortoiseshells and felt a burst of delight to watch the butterfly surge into the sunshine in spring. Interestingly, the released butterfly does not loiter. It flies strongly away, as though hyper-energised by the promise of brightness and freshness of a world renewed by the return of sunshine.

Small Tortoiseshell.©J.Harding.

Happy Christmas

Butterfly Conservation Ireland wishes our members, supporters, friends and your families a  joyful and peaceful Christmas season.

Thank you for your enthusiasm and support during 2017.

Here is a photograph of a beautiful Peacock butterfly, taken on our reserve at Lullybeg, County Kildare on Wednesday 23rd of August, 2017. This lovely butterfly is now tucked up for the winter.

We look forward to seeing this butterfly and many others in the new year!



Winter Cold a benefit for Butterflies

It is December 8th and the Met Office is forecasting a bitterly cold month ahead. How will this impact on our butterflies? Butterflies are regarded as creatures of the light, lovers of sunshine and warmth, vulnerable to the onslaught of bitter winters.  We rarely have cold winters and with climate warming we may get even fewer, so how will this change the fortunes of our butterfly and moth populations? The connection between extreme winter warmth and butterfly population levels was researched by East Anglia University, Butterfly Conservation UK and  the Centre for Ecology and Hydrology (McDermott Long, O., Warren, R., Price, J., Brereton, T. M., Botham, M. S. and Franco, A. M. A. (2017), Sensitivity of UK butterflies to local climatic extremes: which life stages are most at risk?. J Anim Ecol, 86: 108–116. doi:10.1111/1365-2656.12594).

It was already known that butterflies do better in warmer summers but, perhaps unexpectedly, the new research which looked at the impact of extreme climate events on the population of butterflies in the UK from 1976-2012 revealed that extreme mild winters have a negative effect on the populations of just over half of the 41 species studied.  It is interesting to observe that these negative effects occurred regardless of whether the species affected are widespread  species or habitat specialists.  All four of our butterflies that over-winter in the adult form, the Comma, Small Tortoiseshell, Peacock and Brimstone showed a negative impact of extreme winter warmth (disruption of over-wintering in these species may result in losses from predation and decline in fat reserves). Species that showed a similar result and the stage in which these over-winter are the Purple Hairstreak (egg), Dingy Skipper and Dark Green Fritillary (larva) and Orange-tip (pupa).

Only two of the species studied showed that there is a positive effect of warm winters; these were Wall Brown and Holly Blue. Extremely cold winter days were associated with significant population increases in the Large White (over-winters as a pupa) and Ringlet (over-winters as a larva).

Overall, the study found that cold spells in winter were beneficial or neutral in the impacts on population size while warm spells in winter were generally harmful. An additional and unexpected finding is that the pupa of butterflies that have one brood per year show sensitivity to extreme precipitation.

Another recent study, from Stockholm University  also using data from the UK (Stålhandske, S., Gotthard, K. and Leimar, O. (2017), Winter chilling speeds spring development of temperate butterflies. J Anim Ecol, 86: 718–729. doi:10.1111/1365-2656.12673) found that some butterflies that over-winter in the pupal state emerge earlier in the year during a warm spring but not after a warm winter. Three species of the five species studied, Green-veined White, Orange-tip and Green Hairstreak flew earlier in spring after a cold winter. The study found that warm winters delay emergence. This earlier spring emergence might be due to the insect being programmed to emerge from the pupa after experiencing a prolonged period of cold followed by a period of warm conditions; this temperature change process is used to obtain  specimens out of season in captivity. This involves placing a pupa in a refrigerator for some weeks and then keeping it at room temperature which causes early emergence,  mimicking the effects of the passing of winter and onset of spring.

With climate change expected to continue, what  are the main implications for our species? The findings are mixed. Warmer summer weather, as long as drought does not occur, may well help populations to increase and spread. Extreme climate events, such as extreme warmth and extreme rainfall in winter may cause declines. High quality habitats may have the ability to buffer extremes, so it is vital that habitats are managed as carefully as possible to provide the best chance of survival for our butterflies and moths.

When you see the snow and ice over the coming days, please take care, but remember that our butterflies are well-adapted to these conditions which may be necessary for their long-term survival. Snow and butterflies are compatible!

Well managed, landscape-scale habitats may be vital to protect butterflies and moths from climate change.© J.Harding.
The Orange-tip flies earlier in spring after a cold winter but suffers from extreme winter warmth. © J.Harding.



Lullybeg Management Day Report

Weather-reliant activities are hard to plan in Ireland and Saturday 11th November, promised dry two days before, slowly descended into a wearying drizzle.

Undeterred, the Butterfly Conservation Ireland work party knuckled down to do battle with regenerating scrub close to where scrub was tackled last year. Our youngest workers,  Annie and Conor helped by enthusiastically tucking into the work of uprooting birch saplings and cutting young re-growth on willow and birch. Taller material was felled and the resulting cuttings piled neatly to rot down naturally. A great impression was made on the encroaching scrub with these areas now much more open to light, creating breeding sites for grassland butterflies like the Marsh Fritillary, Dingy Skipper and Common Blue.

The process of halting and reversing natural succession (the process of change in biological communities over time) at Lullybeg is needed to ensure that the climax vegetation in much of the managed area of the reserve remains species-rich grassland. Left to develop its climax vegetation naturally, the site will become woodland dominated by birch and willow and its grassland butterflies would be lost. The grassland butterflies and moths specialise on herbs growing in a grassy sward that is open and unshaded. The shading of grassland reduces the light and temperature, making these areas unsuitable for breeding for most of the reserve’s butterflies. Some butterflies, like the Brimstone, breed in open scrub while the Silver-washed Fritillary likes open, sunlit woodland. There are areas of the reserve where the needs of these species are accommodated.  In this way, a habitat mosaic is provided, with a range of habitats scattered throughout the site which are maintained by active conservation management.

Butterfly Conservation Ireland thanks everyone who made a vital contribution to conserving the butterflies moths and other insects on this rich site. We will have another conservation day in February, when we hope for bright spring sunshine!

Marsh Fritillary, a grassland breeder. Photo taken at Lullybeg, on June 2nd, 2017.©J.Harding.
Common Blues, breeders on open grassland. Photo taken at Lullybeg on June 7th 2017, close to where scrub was cut on Saturday 11th November 2017.©J.Harding.
Green Silver-lines moth; this species breeds on scrub at Lullybeg.©J.Harding.

Brown Hairstreak Obsession

The  Brown Hairstreak is one of our most elusive yet most conspicuous butterflies. The adult is rarely seen but the egg is easily found. This paradox may be part of the butterfly’s appeal. Among  butterfly lovers in the UK the Brown Hairstreak has a cult status, evidenced by having its own blog (http://betulae.blogspot.ie/). It is an attractive butterfly, the female especially delightful with a warm  golden  underside with a patch of the same striking hue on the upper-side of the fore-wings.  Aside from the golden patch the upper-sides are  dark brown.  Males look similar, but the underside gold is paler and the fore-wing patch paler and reduced or absent.  The reddish-gold tails on the hind-wings add to its charms. The legs are a striking white, resembling starched white sport socks.

The Brown Hairstreak is the largest hairstreak in Ireland and is not common here or in Britain (we have three hairstreaks; the Green Hairstreak and Purple Hairstreak are the others).  In Ireland it is mainly found in the Burren in Clare and Galway, with a small population in west Tipperary and west of Lough Corrib, County Galway. In Britain it is mainly found further south, in south-west Wales, southern, south-west and south central England with a small population in the east, in Lincolnshire.

The butterfly is single-brooded, flying from late July to mid-September.  It breeds on hedges, scrub and woodland edges.  It needs an extensive area of untidy, lightly or rarely managed habitat containing its larval host-plant, Common Blackthorn. Where it inhabits climax woodland the adult is rarely seen because it keeps to the tree-tops. In this habitat, such as in Garryland Wood, Galway, it frequents Common Ash trees where it feeds on the aphid ‘honeydew’, secreted by aphids feeding on the leaves. This sticky substance coats the leaves when aphids are in abundance, so the adults do not need to descend to feed on nectar.  In years when the aphid secretions are ample, woodland males are rarely observed.

Adults mate early in the day. The rest of the day is mainly spent feeding and basking.  It appears to be a very lazy butterfly; it flies infrequently, preferring to walk from one food source to the next.  Strong wind does not appear to dislodge them. Males occasionally chase each other, but often they ignore each other and mated females. Later in the flight period, typically from mid-August, females disperse to lay eggs on low-growing Common Blackthorn. This is when most sighting opportunities occur. Even then, females do not advertise their presence. Egg-laying females crawl into the interior of a plant probing the surface of young stems for a suitable point, often at the base of a fork, bud or spine, to place her white egg. Occasionally she will deposit two or even three, but usually a single egg is  laid before she flies away to seek another food-plant.  When moving to seek new larval food-plants, she will sometimes cross open ground, and fly well above head height, making the butterfly hard to spot. Plants favoured for egg-laying are often  young, and are in sheltered and unshaded locations.

The egg has a pitted surface, resembling a golf ball. Although a sharp white, it is not easy to find until leaf fall. Then it comes into its own! It stands out against the dark twigs, even in low light. The eggs are  usually placed  below 1.5 metres above ground (although sometimes higher; I observed egg-laying three metres above ground in Tipperary). The eggs are laid from mid-August to mid-September and remain unhatched until leaf burst in April. However, eggs remain on the plant after hatching because the larva only bites a whole in the tough shell to emerge from. I have seen eggs remain on a plant for two years, a testament to their durability.

The larvae are mainly green with diagonal white lines. The larva is slug-like in its shape and, like the  rather languid adult, sluggish in its  movements. In keeping with the adult’s elusiveness, the larva is mainly nocturnal and very hard to find. The pupa too is concealed.  It is formed in June or early July, probably in a crack in the soil or beneath leaf litter or within grass tussocks. It is likely that the pupa has an association with ants.

Where the general landscape’s hedges and scrub are lightly managed over time, annual egg surveys pose interesting questions about the breeding requirements of the species. For example,  breeding sites can receive fewer eggs over time before these eventually fall out of use. Identifying the reasons for this will add to knowledge of the butterfly’s requirements.  Reasons for selection of breeding sites are not easy to determine. In the Burren where tall trees are scarce or absent, the adult feeds low down on hedges containing flowering bramble. While the butterfly breeds on these hedges some adult feeding areas are not used for breeding, even though the larval food-plants and aspect appear suitable.

Last weekend I snatched a couple of hours from an onerous schedule to do a quick egg-hunt at Gortlecka, in the Burren National Park in Clare. On a wonderful mild afternoon I searched a south facing hedge and adjoining patch of scrub where I saw a female lay an egg in August. Within a 20 metre long section of young blackthorn scrub/hedge  I found 16 eggs, a couple just 30 cm above the ground.  Fifteen eggs were laid at or close to the base of a lateral shoot with one laid slightly further up the side shoot,  above three buds.  This patch of scrub has developed in the past five years and this is the first time I have found eggs here, although I  found eggs on the adjoining hedge in previous years. Despite annual searches over more than a decade I have not found eggs on a west facing hedge very close by, despite seeing  females here last August, and in most years from the early 2000’s; however, I have found eggs on west facing scrub elsewhere at Gortlecka. Why it behaves like this is unclear but it is reassuring that the butterfly continues to thrive where I first saw it in the late 1990’s.

Regarding conservation, the species is highly vulnerable to extreme and regular cutting of hedges. While opening up rides in darkening woodland and then allowing plants to re-grow helps the species, annual flailing of hedges is very damaging, as most eggs are laid at the edge of a hedge. In areas where it occurs, rotational cutting should be applied, with large sections, around two-thirds, uncut in any year. It is important to retain patches of young scrub growing a short distance from a hedge or wood edge, as young plants are often favoured by  our rarest hairstreak.

Why are many butterfly lovers so taken with this butterfly? Like many obsessions, the reasons for it may be obscure, but the elusiveness of the adult juxtaposed with the visibility of the egg might be something to do with it. So might timing. What else can a lover of butterflies do during the barren, bleak , unforgiving months from November to March? Egg hunts provide a badly needed outlet for pent-up desire, as well as offering an insight into how well the population is performing.

Brown Hairstreak breeding habitat, Burren National Park, Co. Clare.©J.Harding.
Brown Hairstreak egg, Burren National Park, Co. Clare.©J.Harding.
Brown Hairstreak, female, Burren National Park, Co. Clare.©J.Harding.