Butterfly Season continues in Larval Form

Shadows are lengthening,  temperatures falling and storms Ali and Bronagh dishevelled and drenched the landscape. Butterflies continue to fly but numbers are inevitably falling.

Summer and autumn flowers are fading fast with many species now in seed to feed Goldfinches and other seed-eaters. There is still floral nourishment available with  Common Ivy flowers sticky with nectar and thronging with wasps, flies and some butterflies.  Late bramble and Common Knapweed flowers offer food, while some repeat flowering by Common Dandelion is a cheering sight for late butterflies.

Butterfly sightings continue to be made but records are diminishing. There is a tendency to think that butterflies have vanished until next spring because the free-flying adults are harder and eventually almost impossible to find.

Butterflies continue, mainly in immature forms. Many butterfly larvae are extremely difficult to find in the wild, and a number of species have not been found or recorded in Ireland as wild caterpillars or pupae. I know of just two people who have found wild Purple Hairstreak larvae, and no record of anyone finding Hedge Brown larvae or Wood White larvae, to mention just three species.  This is not surprising. I have taken 20 minutes to locate a Wood White larvae I knew to be present on cut food plant in captivity. Its camouflage is superb. Not only is the larva the same green shade as the leaves and stems of the plant, but it also aligns itself to resemble a leaflet or part of a stem. It is assisted in its concealment by its highly sedentary manner.  The Wood White caterpillar, which leads a solitary life, is feeding now and will pupate late in September or early October. The butterfly will emerge, typically, in May but if there is a cold spring a June/July emergence can occur.

One butterfly that will emerge as an adult this year from the immature forms now present is the handsome Red Admiral. There are many final stage caterpillars and pupae, tented in nettle leaves, out there now. Some adults are emerging now, a process that will continue well into October. The larvae are interesting in that they occur in a range of colour forms, even in the same nettle bed. The colour matters little, as larvae are hidden. This is one of the easiest solitary larvae to find, with droppings often found accumulated in a large leaf below the tented enclosure. Opening the tent will reveal a larva curled in the shape of the number 6. The pupa is a light brown with golden metallic markings. The adult is stunning, especially when seen on a bunch of juicy blackberries or feeding on ivy among the glossy foliage. The adult will hang about for a few days before breeding, or more likely at this time of the year, before heading south to the continent to breed.

The Wall Brown larva is feeding now but finding it is a serious challenge. Features that may help is that it feeds in daylight and basks on bare soil near adjoining grass. The older larva is green with a bluish tint. It loves Red Fescue grass growing in sparse clumps on well-drained soil. Differential growth rates of same-age larvae is a feature of second-generation Wall larvae, with remarkable size variations evident. The fastest growers will sometimes pupate and produce butterflies in October while siblings will take to the air next April or May.  Whether October adults breed successfully in Ireland is not known. It is suspected that resultant larvae may be too small to survive the winter.

The Small Heath’s tiny larva is feeding on the tips of finer grass blades. It feeds during sunshine. It is polymorphic, with green, yellow and reddish-brown forms. This larva is very slow-growing until late spring when growth suddenly accelerates. The first butterflies can appear at the beginning of May given a warm, sunny spring. Generally, adults appear later in May and fly throughout June and much of July. Occasionally late butterflies will be seen in late August and September.

While the larva might be seen as the unglamorous stage in the life-cycle, it is extremely interesting. It is the animal’s growth phase and is sensitive to changes in daylight length, temperature, moisture, the nutrient content of the food-plant, the character of its habitat, changes in the habitat and a range of other factors, depending on the species.  The interaction between the larva and elements in the environment, such as the relationship between some Lycaenid larvae and ants makes the study of caterpillars especially intriguing.  It is the requirements of the larva that often influences whether the species is widespread or highly localised. Finally, in the cooler months of autumn when adults are scarce, larvae offer the butterfly lover a challenge and interest.

Photographs © J.Harding 2018.

Red Admiral larva, pale form.
Wall Brown caterpillar.
Wood White larva on Tufted Vetch.
The Small Heath larva grows slowly. This larva measures 10 mm and is c.90 days old.

September Moths

The great summer weather of 2018 is over but its benefits, it appears, are still being observed. The Small Copper butterfly seems to have produced three generations and a fourth is still possible!

While butterflies being day-flying are easier to monitor, the results of light trapping for moths indicate that some moths are doing well. From the Garden Moth Scheme which covers all regions of Britain and the island of Ireland as one region comes news of very high figures for some species. One recorder had 356 and 131 Setaceous Hebrew Character moths in his two 15W Heath traps. While only 22 gardens in the Republic of Ireland are part of the Garden Moth Scheme these are trapped on over 90%  (97% in May and June 2018) of the nights when trapping is to take place. This high level gives credibility to the results.  For 9 out of the 12 regions in the British Isles, the Heart and Dart moth was the most numerous garden moth on average for May and June 2018. (Scotland and North-east England (Hebrew Character) and the Channel Islands (Diamond-back moth) are the exceptions).

We are now looking forward to seeing how the autumn species perform, and last Friday night saw my first record of the Beaded Chestnut,  a moth that variable in appearance and often quite numerous during its flight period. The appearance of this moth is one of the signals that the autumnal moth species are about to appear. Other moths which occur now include the Setaceous Hebrew Character, a distinctively marked species whose larvae are found on Common Nettle and two more colourful species, Frosted Orange and Pink-barred Sallow. The Frosted Orange larva feeds on thistles leading one to expect it to be far more numerous than it is. In fact, it is recorded in low numbers, and cannot be assumed to appear in gardens every year. Its ginger peppering,  yellow oval markings and brown band means it is attractive and unmistakable.

The Pink-barred Sallow is another pretty species. It shows a broad pink band across canary yellow forewings as its prominent marking with pink mottling above and below the band with the forewing edge pinked out in pink. While it occurs more frequently than the Frosted Orange, small numbers are the norm in my garden. Willows and poplars are the caterpillar’s food plants.

In good habitats, some night-flying moths can sometimes be seen during the day. These are usually observed in tall flower-rich grassland in warm, overcast weather. It provides a rare opportunity to see some species that otherwise can only be attracted to light traps. Like the butterflies, these moths will be found feeding on flowers, especially Common Knapweed, Common Ragwort and Devil’s-bit Scabious. The Silver Y moth flies during the day and night and is very fond of nectar, and will be seen with its typically swift buzzing flight at flowers, fluttering while taking nectar.

To encourage moths to breed in your garden, Grey Willow Salix cinerea and Downy Birch Betula pubescens,  native oaks Quercus robur and Quercus petraea, Common Hazel Corylus avellana, Common Blackthorn Prunus spinosa, Common Hawthorn Crataegus monogyna and Common Nettle Urtica dioica are strongly recommended. Planting a species-rich hedge consisting of these tree species might be used to build a habitat in a smaller garden. A large garden allows room for some trees to develop without cutting and this may be more fruitful as some butterfly and moths need tall trees. A garden such as that shown below can be developed to resemble a woodland clearing, with trees, scrub and or hedging surrounding a grassy area containing native flowers. This offers food, shelter and warmth, creating ideal breeding conditions for many moths and butterflies. And a life-filled, exciting place for you, too.

Photographs © J. Harding 2018.

Setaceous Hebrew Character, numerous in 2018.
Beaded Chestnut, an autumn moth.
Frosted Orange, an uncommon moth in gardens.
Pink-barred Sallow, a beautifully marked moth.
Gardens planted with a range of native trees, shrubs and herbaceous plants are rich in moths.

September Butterflies

September 2018 opened with sunny days and warm, still nights, ideal for diurnal and nocturnal Lepidoptera. Numbers are still high but the number of species on the wing is falling as we move into autumn. The moth catch in my garden on August 31st consisted of moths that are typically found mainly in summer although many of these were worn. An extraordinary number, for me, was 222 Square-spot Rustic moths. Never have I seen one moth species in such high numbers on a single night. The high number is most likely the result of a great summer. By August  31st 2017, I recorded 1,502  moths in 21 trapping sessions running from March. By August 31st 2018 I recorded 2,358 moths in 22 trapping sessions.  The increase is probably related to the much warmer conditions experienced during the late spring and for most of the summer this year. The benefits of larger numbers of moths are enjoyed by our bat and bird populations. I am thinking of the 34 Common Pipistrelle Bats and the 40 or so Brown Long-eared Bats that have occupied my attic for much of the summer.

Unfortunately for day flying butterflies, my garden Robin and Wren are keenly aware of the butterflies available. In particular, the birds are snapping up two species, the Small Tortoiseshell and Peacock.  The speed with which a Robin attacks is impressive and while it often seizes the outer part of a forewing instead of the head,  cumulative wing damage reduces flight proficiency and increases the chance of capture.  One Small Tortoiseshell was found dead with no sign of injury. Was it stung by a wasp?  The dramas are compelling to watch and speculate on, but concentrations of prey must lead to high predator activity and high mortality. However, in the case of the fiercely territorial Robin,  high availability of butterflies does not lead to a higher number of Robins to prey on them. Furthermore, some butterflies seem to evade birds. From my observation, the birds in my garden either ignore or cannot catch the Painted Lady and Small Copper!

On September 5th a new Small Copper appeared in the garden, dazzlingly copper in the sharpening late afternoon sunlight. The veteran who has been in command of the perch post on a tall ragwort for most of August encountered the new male and battered him away. The new boy must wait his turn! In the evenings I check the shed to count roosting Peacocks and Small Tortoiseshells. The door is left ajar for them and I hope they decide to pass the winter there.  Sometimes the Robin goes into the shed too but perhaps the bird has not located the butterflies yet. When the warmth is gone for 2018, the shed door will be shut and the butterflies will be beyond his beak until they depart in spring.

Butterfly numbers in gardens appear to be up on last year and they are abundant in other habitats too. While there may not be as many Painted Lady butterflies this year numbers are quite high. Quite often a good year for this butterfly such as 2017 is followed by much smaller numbers the following year but this has not been the case in 2018 on sites I visit or further afield. From Northern Ireland comes a figure of over 100 seen by Ian Rippey on the County Down coast on August 29th. Recent records suggest that these powerful migrants are more numerous than adult Red Admirals at the moment but there are many Red Admiral larvae still developing, suggesting a good flight of the species later in September and October.

There are still Large Whites, Small Whites and Green-veined Whites around but numbers of these are declining as the season nears a close, but where it occurs, the Brimstone, which overwinters as an adult, is quite numerous.  On Saturday, September  1st I saw around 30 of these lovely butterflies apparently hanging suspended on flowers on a cutaway bog in the glorious sunshine. The Common Blue and Holly Blue still fly, as does the Small Copper while in the Burren there may still be some Brown Hairstreaks around.  I saw two late Silver-washed Fritillaries on September 1st and one the following day, all males. Speckled Woods are jinking around hedges in good numbers in many areas, and their numbers often peak in mid-September in parts of the west and the Midlands. This butterfly can sometimes extend into early November. Along the west coast newly emerged Meadow Browns confuse observers from the east of Ireland who are accustomed to seeing this butterfly virtually disappear there by mid-August. In some years Clouded Yellow butterflies arrive in small numbers in September and October, giving a final flourish to the butterfly flight season.

We often enjoy beautiful September weather and if so, some short-lived butterflies may live longer, butterflies that over-winter as adults may fly longer and some species may even fit in a partial late generation. Ireland may also get some late migrants.  At such times of plenty, we can be persuaded that summer is still with us, and will continue to beam warmly on us. But enjoy the butterflies. We know the cold will banish them soon!

While the comparative analysis of the figures for garden butterflies will be published later, in the Annual Report 2018, it is evident that most species are present in higher numbers in many gardens than in 2017. If you would like to take part in our garden butterfly survey, the details and survey form can be found here:  https://butterflyconservation.ie/wp/butterflies/gardening-for-butterflies/

All photographs © J.Harding 2018.

At this time of the year, the Painted Lady feeds to prepare for migration. In years when it is abundant, high numbers can be present in flower-rich habitats in early September.
The Speckled Wood, a hedgerow and woodland butterfly flies from April to November with some short periods of scarcity during its long flight period.
Female Common Blue basking, Kildare.
Small Whites mating. Egg-laying is taking place now.
The Brimstone engages in prolonged pre-winter feeding during good weather in September.
A newly emerged Small Copper.
The Small Tortoiseshell basks during cloudy spells. When direct sunlight returns, the butterfly resumes its pre-winter feeding.
The Clouded Yellow may arrive from Europe in September and October.