The Hunchback of the High Weald

Posted by Graeme Lyons , Tuesday, 23 June 2020 14:20

The last time I saw a hunchback fly was five years and one day ago on 21st June 2015 when I last surveyed the private estate of Wadhurst Park. This is the nationally scarce Ogcodes pallipes and yesterday I beat this adult from there. Reading up in Stubbs & Drake, it's interesting to find out that this clumsy looking thing is a parasite of spiders! Unlike the more familiar external parasites though, this one develops inside the abdomen. The host spiders listed seem to be mainly ground-dwelling species. The grassland where I found this (actually it was beaten from an elm) was thick with spiders in the sward, overwhelmingly dominated by Neoscona adianta. I would say at a greater density than anywhere else I have surveyed. All the ID features to key this out from the other two in the family are visible in this photo. 

Very soon after this, I swept what I assumed was a male, as it was half the size. I actually realised that this was one of the other species of hunchback fly! This is the nationally scarce Acrocera orbiculus, and a new one for me! Later on that day I beat another one of these from Gorse, actually it was dead in a spider's web. A weird kind of symmetry there. So three hunchback flies in one day. Why here? I have surveyed plenty of dry grasslands with a wealth of spiders over the last decade and have not seen one of these anywhere else. Is it because of the altitude and actually these are more north western species? 

Other highlights included Andrena labiata, Stelis ornatula, Theridion pinastri (new to East Sussex!) and this striking little micro Euspilapteryx auroguttella that I swept off Slender St. John's-wort. It's much more metallic than I was expecting and seems to be quite scarce in East Sussex.

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