Spring 2012 newsletter - Butterfly Conservation

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The Trials of a White-letter Hairstreak Douglas Goddard The White-letter Hairstreak had a good season in 2011. Observers sent in records of larvae found on Wych Elm in Daventry and Boughton, the adults were seen from 10th June until 28th July, and several new sites were discovered, notably Wicksteed Park. In Fermyn Wood, there are a number of elm trees, some of which provide sightings of White-letters reliably each year. One lies at a ride intersection in Cherry Lap, and here, at the beginning of July, pupae were to be found under the leaves and good numbers of the adults were emerging and laying eggs. Commas also use the tree as a foodplant and their larvae were also easy to find here. The dark pupa While searching and photographing Comma larvae on 4th July, a White-letter pupa was still to be seen, long after the emergence of others. Dark brown in colour, it had clearly been parasitized and was not going to hatch. I decided to take it home to note further developments. A week later, sure enough, a small wasp emerged from the pupa, sawing off the end to make its exit. I photographed the specimen and sent it to Mark Shaw at Edinburgh. He identified it as a female of Virgichneumon tergenus (right), a known, 6 but rarely collected, parasitoid of the White-letter. It attacks the host in the pupal or prepupal state, so is only found in pupae. It has been reared from Black Hairstreak (Perkins’ Royal Entomological Society Handbook), and the National Museum of Scotland has specimens from Silver-studded Blue, Common Blue, satyrium esculi (from Spain) and three from White-letter Hairstreak, including mine. The hibernating strategy of this wasp is not known; if it, presumably, over-winters as an adult, only the female will do this, having mated beforehand. On 1st October, Andy Wyldes and I visited the wood again, looking (unsuccessfully!) for Purple Emperor larvae. As we walked through Cherry lap, the work of the Forestry Commission was much in evidence, the lower branches of sallows and other trees having been hacked away by mechanical cutters to make the route clear for lorry access. Our favourite elm had not been spared this destruction, several of the lower branches lying in a heap on the ground. We searched the branches and found a couple of eggs and cleared the remaining ones into a heap to look through later. That evening I took a few of them home and searched them, discovering eight more eggs. Closer inspection revealed that three of these had exit holes made by another parasitoid, a tiny wasp. The rest will be kept and hopefully reared in the spring to be released as adults, along with any others we find among the remaining branches later on. Predation of butterflies in their early stages is widespread, and these discoveries serve to remind us that it can be extensive in some years. Of a hundred eggs laid by a female butterfly, only two must survive to adulthood, to replace the original pair which mated and keep the population level stable, so normally species
The White-letter Hairstreak eggs with exit holes can cope with these natural enemies. Occasionally, as in the case of the Small Tortoiseshell and the arrival of Sturmia bella, the balance can be changed 7 dramatically. The population cycle of the Holly Blue is well documented, determined by a host-specific parasitoid. The destruction of habitat is another matter altogether. Perfectly healthy eggs were lost by flailing the branches of this elm in Fermyn Wood and, although the higher reaches of the tree were not affected, the lower levels are no longer available for egg-laying White-letters and Commas and for us to see the early stages within reach. The potential survival rate of the eggs collected should be higher than in the wild, at least addressing the balance for this year, but here is a reminder of how precarious life is for our butterflies. Wider Countryside <strong>Butterfly</strong> survey Clare Topping, a member who lives in Daventry, has kindly agreed to co-ordinate the WCBS for Beds and Northants, a position which has been vacant for the past year since Julian Bull left to live in Norfolk. We extend many thanks to those members who recorded a square last year. Branch participation in the scheme was down in 2011 compared with previous years, so we are looking for more people to take part this summer. Please contact Clare by email: ctopping@ratfox.net for more information and to allocate a square near where you live. Clare will be contacting previous participants shortly. Please let her know if you are willing and able to survey your square again, indicating the Grid Reference.
Page 1 and 2: No 80 Spring 2012 www.bedsnorthants
Page 3 and 4: Butterflying in the Pyrenees Greg H
Page 5: The weather cleared slightly and bu
Page 9 and 10: Silver-washed Fritillary Photo Doug
Page 11 and 12: Butterflies in Kefalonia David Chan
Page 13 and 14: Field Trips 2012 Northants Sunday,
Page 15 and 16: November 13 th 2011 Sunday, January
Page 17 and 18: Butterflies of Northamptonshire The

Spring 2012 newsletter - Butterfly Conservation

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