During my Garden Bioblitz of the the 6th June, I found a moth case on a cotoneaster leaf. I tried to identify it by using this webpage and I thought it looked most like Coleophora trigeminella. I was very excited by this as the species hasn’t been recorded on Cotoneaster in the UK before, only in Europe. Could I have discovered a new foodplant for this species in Britain?
I emailed the Surrey moth recorder, Mr Graham Collins, with news of my finds. I asked him whether it was likely to be Coleophora trigeminella or something else. He kindly responded saying that he didn’t think that the larval case belonged to this species but Coleophora serratella which is ‘probably the commonest species of British Coleophorid’ according to the UK Moths website. I was quite disappointed!
However, why was it on a cotoneaster leaf? The larvae usually feed on hazel, birch, elm or alder. It is most likely that the larvae fell from the foodplant (there is a birch tree straight above the cotoneaster) on to the leaf where it formed the case, or the larvae wandered off the leaf looking for a better place to create its case.
When I returned to the same leaf nearly a fortnight later, on the 18th June, I was given a huge surprise. The adult moth had emerged from the case overnight and was resting parallel to the case! It was so fresh in fact that the antennae were not resting forward in the typical coleophorid fashion but running backwards along the body! I sent this photo to Mr Collins.
I thought that it was too light for Coleophora serratella and the ochre colour matched Coleophora trigeminella. Could I have found a species of moth that hasn’t been seen in Surrey for nearly half a century? Unfortunately that was not to be the case. Mr Collins responded writing that he now thought that the moth is either Coleophora flavipennella or Coleophora lutipennella. The larval stages of both of these moths feed on oak leaves, which makes sense as there are several large oak trees which also have branches above the cotoneaster bush. The larva probably fell from the leaves.
However, it is not possible to separate moths of those species without examination of the genitalia. For this I sent the moths off to Mr Collins by post and he kindly looked at them under the microscope. The genitalia point to Coleophora flavipennella, which I think might be the least common of the pair although I am not certain. The genitalia of C. flavipennella look like this:
Compared to the genitalia of C. lutipennella:
There is quite a lot of difference! This is a new species for me and I hope this blog post shows that often identification is not that straightforward.
(genitalia photos from http://www.mothdissection.co.uk)