Colourful in-flight entertainment

MY comments about brown-tail moth webs last month produced quite a lot of feedback. That is the moth with caterpillars able to shed hairs which can cause allergies in humans. It has been present at Spurn for a number of years and small numbers have been seen further north. Several readers reported what appeared to be similar infestations in inland parts of the county.

However, there are a number of moth species which use webs as communal homes for caterpillars. These can also completely strip a group of trees or a length of hedgerow. Most belong to a group known as the ermine moths. Fortunately, they are not dangerous to humans, and in most cases the trees and shrubs recover, although this may not be fully evident until the following year. The webs are usually much smaller than those of the brown-tail.

Late July to early August usually sees the biggest peak of the year in butterfly numbers, especially for those which visit gardens like the peacock and small tortoiseshell. But as always with butterflies, an awful lot depends on the weather. Not only the weather locally, but also on the continent, as that controls the degree of immigration.

Some species are great travellers, and on a hot July 19, just as a growing number of our local species were beginning to appear, we had what looks like a boost from the continent.

Observers at Spurn experienced an arrival of small and large whites together with peacocks flying in from the south-east and passing observers at the rate of 120 per minute. It looks like a lot of extra butterflies arrived in the county that afternoon.

One sedentary species which does seem to have done quite well is the marbled white, a speciality of the chalk grasslands of the Yorkshire Wolds. It usually flies from early July to early August. Although called a 'white' it is actually a member of the 'brown' family. Seen close to, it is very striking in black and white, but from a little distance the pattern breaks up its form and makes it quite difficult to spot.

Sally Whales sent me a beautiful picture taken in Leeds of a white-letter hairstreak in her garden. This is one of several 'treetop' butterflies, which although not uncommon, are rarely seen unless you know where to look and what to look for. It is usually found on or near wych elms.

I generally spend several hours each year gazing up through binoculars at trees where I know there are colonies.

If I am lucky I might catch a brief glimpse of a small brownish butterfly moving high up amongst the branches. They do occasionally come down to ground level to nectar on flowers in the middle of a warm afternoon, but you don't often see this. So Sally was particularly lucky, especially as she had it in view for some time.

My closest encounter with a white-letter hairstreak was on Withernsea promenade a few years ago. It was overcast, blowing a gale and not a day I expected to see any butterfly. But there it was, just about to be blown out to sea. I made a lucky snatch and caught it bare-handed.

I could hardly believe my eyes when I realised what I had caught, the nearest known colony being miles away. But then if you are a treetop butterfly you run the risk of being blown away in a July gale. At home, I caged it with some suitable flowers and it sucked up the nectar avidly.

In better weather a couple of days later I took it to a known colony and watched it fly high into a wych elm. A very lucky butterfly.

Howard M Frost is Butterfly Conservation's voluntary organiser of butterfly recording in Yorkshire and can be contacted via their website, www.yorkshirebutterflies.org.uk where you can also find daily updates as to which butterflies and moths are being seen across the county.

CW 24/7/10