Friday, 27 June 2014

Shades of green ...

Dark Green Fritillary (Argynnis aglaja)

The Dark Green Fritillary (A. aglaja) is the most widespread fritillary found in the British Isles. Its name is derived from the green hue found on the underside of the hindwings, which are peppered with large silver spots. This butterfly can be found throughout the British Isles, although it is less common in central and eastern England. Outside of central Scotland and southern England, it is most frequently found in coastal areas and is the only fritillary found on Orkney and the Outer Hebrides. Despite its powerful flight, it is somewhat surprising that this species is not particularly mobile, generally staying within its breeding grounds.

A freshly emerged male prepares for flight ...


More at:

www.ukbutterflies.co.uk/species.php?species=aglaja

Tuesday, 24 June 2014

Finding mnemon ...

Mountain Ringlet (Erebia epiphron)




The Mountain Ringlet (E. epiphron) is probably one of our most difficult species to see. It is only found in discrete colonies in remote locations, has an extremely-short flight period (a few weeks only) and can be difficult to find in anything other than warm bright weather, since the adults tend to remain sheltered deep in grass tussocks in overcast and cool conditions. Given the right temperature this butterfly will take to the air as soon as the sun shines, bringing an apparently dormant landscape to life. As its name suggests, this butterfly is found in mountainous areas, typically at altitudes between 450m and 800m AMSL though can be found at both lower and higher levels; as per the example figured (from around 350m AMSL). E. epiphron forms discrete colonies in particular areas of the mountains they inhabit and, on good sites, may be seen by the hundred. This is typical of epiphron - localities may be few and far between, but where they occur the butterfly is often found in abundance.

E. epiphron is found in two main regions in the British Isles. In England, it is found in the Lake District of Cumberland and Westmorland. It is also found in western central Scotland, primarily in the counties of Argyllshire, West Inverness-shire and Mid Perthshire with a few scattered colonies elsewhere. It is surprisingly absent from Snowdonia and the Pennines. On the basis of four specimens in total (seven are reputed, with four considered by most authorities to be genuine), this butterfly is also thought to have occurred in Ireland (see references below).

There is one generation each year, with adults emerging at the start of June in the Lake District and early July in Scotland.

A recent visit to Irton Fell, with my good friend Peter Eeles, produced numbers in excess of 150 (a male is figured above), with the peak of sightings being achieved on the higher slopes close to Greathall Gill and Whin Rigg. We were particularly pleased to watch a female ovipositing on Mat-grass (Nardus stricta). The eggs, which are pale cream at first, develop red-brown blotches after a few days. They are relatively large compared with the size of the butterfly, with each female laying up to 70 eggs. This stage lasts around two or three weeks depending on the weather

A beautiful butterfly in fabulous surroundings …

More at:

Monday, 23 June 2014

Summer evenings and stiff necks ...

Purple Hairstreak (Favonius quercus)



The Purple Hairstreak (F. quercus) is our commonest hairstreak, and may be located in oak woodland throughout southern Britain, and more locally elsewhere. It is often difficult to locate, due to its habit of flying high in the tree canopy, where it feeds on honeydew; groups of several individuals chasing one another is not an uncommon sight. However, the adults are occasionally seen feeding and basking at lower levels, on various small trees, shrubs and bracken. This butterfly is found across southern England and Wales, with scattered colonies further north. It is also found in parts of Ireland, mainly between Wicklow and South Kerry.

It is primarily found in woodland containing oak trees, the foodplant of the larva. However, the species can be found in any location where oaks occur, including lanes, parks, gardens, and other urban areas. The primary larval foodplants are Pendunculate Oak (Quercus robur), Sessile Oag (Q. petraea) and Turkey Oak (Q. cerris). Evergreen Oak (Q. ilex) is also used.

Eggs are laid singly (or less commonly, in groups of 2 or more), usually at the base of a plump oak bud, or cluster of buds, but can also be found on an adjoining twig and at various heights. They are laid on branches that are sheltered and receive full sunshine - such branches are therefore on the southern side of the tree. There also appears to be a preference for solitary trees, such as those found at the edges of woods, or those that form part of a hedgerow. Eggs are also most-often found on relatively mature trees (since these have the plumpest buds) on branches that are twisted and gnarled. Eggs are relatively easy to find in suitable locations during the winter months before the oak buds burst. Emergence occurs from the last week of June, through July and into August, with adults still being found into September. There is generally a peak at the end of July and early August, or later in Scotland. There is one brood each season.

Check out the oaks near you ...

More at:

Sunday, 15 June 2014

The prophetess ...

Marsh Fritillary (Euphydryas aurinia)


This delightful butterfly, a female pictured above, is one of our most threatened species and has suffered severe declines in recent decades. Although declining throughout Europe, the British Isles is considered one of the few strongholds for this species. However, the reclamation of wetlands and the ploughing up of downland has meant that E. aurinia has now disappeared from many counties and has also suffered severe declines in the British Isles; this butterfly is therefore a priority species for conservation efforts. Although still widespread in some parts of its range, this butterfly is reputedly declining by over 10% each decade. The deteriorating fortunes of this species are believed to be the result of inappropriate habitat management, coupled with the need for sufficient habitat for the butterfly to form meta-populations, where local extinctions can be reversed by recolonisation from neighbouring colonies. It is currently found in southwest England with a small population in northwest England, the islands of southwestern Scotland and the adjacent mainland, and northwest and southwest Wales. It is also locally widespread in Ireland.

On a positive note, aurinia is an easy species to breed in large numbers in captivity and one, which lends itself to reintroduction or establishment in suitable areas where its main foodplant, Devil’s-bit Scabious (Succisa pratensis), grows in some profusion. My late good friends, the respected entomologists Peter Cribb and Peter Taylor, both kept healthy stocks of this species going for well over 25 years and bred thousands of healthy specimens for release purposes in various counties in the south of England. In Sussex, the former Ditchling Common colony originated from this source with the original stock coming from just over the border in Surrey.

Colonies of E. aurinia are known to fluctuate wildly in population density. It may be present in good quantities one year, only for the population to crash dramatically the following season without any apparent reason - before recovering just as unexpectedly. It does not do well in adverse weather conditions and can suffer significantly from the attentions of parasitic hymenoptera during the larval stage. Adults, which typically emerge in the middle of May, reach their peak in early June. In northern Scotland they emerge slightly later. There is one generation each year.

Where it occurs, aurinia uses several different types of habitat, including chalk hillsides, heathland, moorland and damp meadows. A factor common to all habitats is that they are in full sun, their higher temperature aiding larval development. As previously mentioned, the primary larval foodplant is Devil’s-bit Scabious (Succisa pratensis). Field Scabious (Knautia arvensis) and Small Scabious (Scabiosa columbaria) are also used.


On emerging from their eggs the larvae spin a silk web, by binding together leaves of the foodplant, in which they live and feed. Larvae build new webs as they grow and even move to a new plant if necessary. In later instars, the webs can be quite conspicuous. Larvae will also bask on the outside of the ‘tent’ absorbing the sun's rays, where their increased temperature aids digestion. After the third moult the larvae build a dense nest of silk low down in vegetation in which they hibernate. Larvae will emerge from their nest with the onset of spring and can be seen basking in warm sun as early as February. The larvae eventually split into smaller groups, continuing to build silk webs where they bask communally to keep their body temperature relatively high, even on cool days. More-mature larvae tend to feed alone and are often found wandering across open ground looking for their next meal or, eventually, a pupation site. There are 5 moults in total. The pupa (pictured above) is formed head down, attached to a twig or plant stem by the cremaster. The pupa is essentially white, with a beautiful mix of black, brown and orange markings. This stage lasts between 2 and 4 weeks, depending on temperature.

More at:

Thursday, 5 June 2014

Against the trend …

Agapanthia villosoviridescens


The Golden-bloomed Grey Longhorn (A. villosoviridescens)

The Cerambycidae, the Longhorn beetles, are a very impressive group of insects. The family, which includes some of Britain’s most impressive beetles, currently numbers around 70 species. Many striking examples can be found abroad. They are predominantly beetles that develop in wood, with the adults being active during the spring and summer months. However, A. villosoviridescens is an exception to this rule, developing in the stems of a variety of herbaceous plants including Cardus, Urtica, Angelica, Chaerophyllum, Artemisia, Salvia and Aconitum. The larvae develop in the above-ground plant tissues. They cut off the plant stalk before pupation, create the pupal cells near ground level, and the adults leave the stalks via a newly created exit hole in the side of the remaining stalk. The above specimen, one of four observed, was found sitting on Hemp-agrimony (Eupatorium cannabinum) at a West Sussex wetland site.

My first encounter with this impressive species …

Sunday, 1 June 2014

Stoned ...

European Stonechat (Saxicola rubicola)


The European Stonechat (S. rubicola) is a fairly common resident and partial migrant to Sussex. They are associated with two main breeding areas: heathland and downland with gorse and scrub. Ashdown Forest in East Sussex holds about 50-70% of the county total of circa 150-200 pairs; this out of a national population of circa 56,000 pairs. They are typically seen perching on the tops of bushes in otherwise rather open places, with favoured locations being regularly visited.

An attractive bird and one that is always a pleasure to see …

References:

Scott-Ham, M., 2014. European Stonechat. The Birds of Sussex. Thetford: British Trust for Ornithology (BTO) Books on behalf of the Sussex Ornithological Society, pp. 518-519.
Scott-Ham, M., 1996. Stonechat. Birds of Sussex. Sussex Ornithological Society, pp. 424-425.