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Dolichopus agilis

Submitted by Ray Morris on

Following on from my earlier general enquiry re Dolichopodidae records in VC55 I am now concerned about the veracity of my records of Dolichopus agilis in the county.

I took this several times during malaise trapping at several locations in the Rutland Water NR in the period 2014-2016 and I have since found it in Rothamsted light trap material at the Loddington (East Leics) site. At RW both sexes were taken but only females at light.  I have only two other records - one from a churchyard in west Leics and another by Andy Jukes from a site in north Leicester 2018. 

I was unaware of the apparent scarcity of this species (according to the current NBN Atlas entry) and so wonder have I mis-identified the species (I used the Fonseca keys) or is the fly under-recorded in Britain? Any help in solving this dilemma would be welcomed!

Naturally, if I come across it again this year I shall keep specimens!

 

Comments

There are only 3-4 yellow-legged Dolichopus with just one seta on the hind basitarsus so in theory it should be possible to make a correct identification for both sexes using Fonseca, although I've not been able to check this. Do hold on to any more specimens since it is genuinely uncommon. And maybe your identification was right.

But .... I have few records of agilis in the E&D scheme database, and they are scattered thinly across England and Wales in a manner that suggests plenty of incorrect identifications - scarcer species are not usualy smeared evenly across the country. I've never found it. There are no convincing females in the NHM London or Oxford Mus (the only one in London, in their World Collection, appears to be simplex; the one at Oxford has 2 setae on hind basitarsus). The only male in these museums (at Oxford) has lost most of its hind legs so I cannot verify Fonseca's key. The other male at Oxford has been placed upside-down, presumably by Fonseca, so he didn't agree with this det. So a bit of a mess.

Thanks Martin for your thoughts.  I have resolved to keep any dolis that I come across this year!

 

I came across a paper that separated  Hercostomus species into several groups (femora colour, postocular colour, antenna colour)  but only members of group 3 were listed.  Is there a list of British species that have been allocated into this grouping scheme - it does seem a useful way to approach the genus.