Chasing clouds ...

Clouded Yellow (Colias croceus)

The Clouded Yellow (Colias croceus) is primarily an immigrant to the UK, originating from North Africa and southern Europe, with numbers varying greatly from year to year. Each season, we normally see at least a few reaching our shores and, occasionally, they arrive in large numbers; such as the estimated 36,000 that appeared during 1947 when good numbers of much rarer migrants, such as Bath White (Pontia daplidice) and Pale Clouded Yellow (Colias hyale), were also recorded.

In more recent years, it has been shown that this species has successfully overwintered in the south of England. However, it is believed that the majority of individuals perish, since both larva and pupa of this continuously-brooded species are easily killed by damp and frosty conditions. In good seasons, C. croceus can produce up to three generations in the UK. In flight, the orange-yellow colour is quite distinctive, and unlike any other species. The pale helice form, occurring only in the female, is a creamy white, rather than yellow in colour and may lead to confusion with other similar species.

This strong-flying species always settles with its wings closed and so the dark borders on the uppersides of the wings are only clearly visible when in flight or when viewed backlit at rest. There is no elaborate courtship and, having mated, the female is subsequently able to lay an extraordinary number of eggs; up to 600 have been recorded from a single female.

Two females from 2013 above ...

Precious metals ...

Surrey Downland, 30-31 July 2013

The Silver-spotted Skipper (Hesperia comma) is a warmth-loving species. Its range contracted during the 20th century due to a reduction in grazing stock as well as the onset of myxomatosis in the early 1950s, which severely affected rabbit populations; the butterfly requiring closely-grazed chalk downland sites on which its primary larval foodplant, Sheep's-fescue (Festuca ovina), grows. Recent years have been more promising and this is one of the few species that is increasing its range. It is still relatively-local, with current strongholds being located in the Chilterns, Hampshire, the North Downs between Guildford and Reigate, East Sussex and south-east Kent. It occurs locally in my own county of West Sussex and is currently showing a positive trend for expansion into adjacent suitable habitat.

It is easily identifiable, since it is the only golden skipper found in the British Isles that has the distinctive white spots on the underside of the hindwings, which give the butterfly its name. Like other ‘golden’ skippers, the male is distinguished from the female by the sex brand on its forewings, which is a line of specialised scent scales.

H. comma is one of the latest species to emerge, typically not appearing until late July or early August, and it is then on the wing until early September. There is one generation each year. Like most skippers, this is a fast-flying species that flies close to the ground, and can be extremely difficult to follow when in flight. Both sexes spend the majority of their time either basking or feeding, and a wide variety of nectar sources is used. The butterfly will find the warmest patches of ground on which to bask, enjoying the warmth of paths, rabbit scrapes and other patches of bare earth, which have been baked by the sun. The males rest on suitable sunlit perches, and will investigate any passing butterfly, in the hope of finding a mate. If a virgin female is encountered, the pair exhibits a tumbling courtship, with the male eventually forcing the female to the ground where mating takes place. An egg-laying female locates a suitable patch of bare ground, such as a rabbit scrape, and then walks to the edge of the patch looking for a suitable location on which to lay a single egg.

A female at rest pictured below ...

Coridon ...

Surrey Downland, 30-31 July 2013

Simply wonderful …

I recently spent two days, with good friend Nick Broomer, searching several areas of chalk grassland on the beautiful Surrey downland; our targets, the beautiful Silver-spotted Skipper and the enchanting Chalkhill Blue. We were not to be disappointed on either count.

Although Tuesday was accompanied by persistent rain for much of the day, an early morning arrival provided ideal conditions for searching the grassland for roosting butterflies; we were not disappointed and found many hundreds, probably thousands, of roosting Chalkhill Blues over much of the hill. This included a number of nice aberrant specimens including those pictured in the two images below, referable to ab. postcaeca, Bright & Leeds (1938). The first image shows a particularly well-marked male which we observed from shortly after emergence until its first flight. Wednesday started warm, and by midday large numbers of insects were on the wing. As the sun pushed through the clouds the numbers of Chalkhill Blues increased and we were privileged to witness a magnificent display as the air and ground around us turned blue as if covered in tiny sapphires. It is difficult to estimate actual numbers, though if I were pressed to do so, there were certainly many thousands and probably many tens of thousands on the wing; possibly many more. Although I didn’t witness the peak of the Sussex Chalkhill Blue explosion last year, Wednesday’s display was an event to remember ...

A privilege to have shared with a good friend …