A diary of my mothing activity covering highlights and photos from my moth trapping activities. Mainly Norfolk (UK), occasionally beyond. I may mention other wildlife sightings here, especially insects, but for birds see my birding diary.

Sunday, 19 June 2016

An unusual Bryotropha form

On 8th June I headed up to Burnham Overy to look for birds.  Naturally I didn't restrict my looking to birds.  Some 240 Diamond-back Moths Plutella xylostella were presumably only a fraction of what had been there in recent days.  32 Plain Fanners Glyphipterix fuscoviridella were the next most numerous moth, excepting the Spindle Ermine Yponomeuta cagnagella larvae.  Other moths were 5 Carnation Tortrixes Cacoecimorpha pronubana, 2 Hook-streaked Grass-Veneers Crambus lathoniellus, Common Carpet, Yellow Shell, Brown-tail larva and 7 Cinnabars.  There was also an interesting Gelechiid which I didn't recognise.

This pale buffy-coloured moth had conspicuous large but poorly-defined dark spots on it and I couldn't think of any Gelechiid showing such a pattern.  Some have smaller better defined spots, or spots arranged differently, but nothing obvious fitted.  It didn't get any clearer when I looked through books and various internet resources.  Was I right about thinking it was a Gelechiid?  Taking it through the Kleine Vlinders key proved that I was - this was definitely a Gelechiid so I was looking in the right place.  Time to look at its genitalia.  That should pin it down I thought.  Well it probably would have done more quickly if the dissection had gone smoothly, but for those of you who don't do dissections the process involves soaking it in warm acid for a while then cleaning the gunk off to reveal the relevant bits of genitalia.  Sometimes, as this time, the gunk proves a bit hard to remove and the genitalia get damaged in the process.  I was left with a few pretty mashed up and not very well cleaned bits of genitalia, but I had the important bits - it should be ok.

I looked through all the images in MOGBI - the best reference book I have for Gelechiid genitalia, and all those on the Dissection Group website, but couldn't find a good match.  But it did help narrow it down - it was a female Bryotropha (which made sense - the shape of the moth was very Bryotropha like, just the pattern quite unlike any I knew).  Moreover the female genitalia of Bryotropha split into two types, broadly-speaking, so I could rule out the likes of desertella etc. which in some ways would have been the better match externally.  Closest were basaltinella, affinis, similis and umbrosella.  It was a pale thing with dark spots so obviously not affinis or similis.  I'm not familiar with umbrosella but a quick look at images of that showed it to be another dark species.  So basaltinella?  I could just about imagine a really worn basaltinella looking a bit like this, but it seemed a real stretch.  And there have only been 2 Norfolk records of basaltinella (both in my garden) and the habitat of the dunes didn't seem right.  And the genitalia weren't right either.  Could there be another species not featured in MOGBI?

I look at the Lepiforum website in these instances - they cover a broader selection of European species.  Next to basaltinella was plebejella, a southern European species that is pale buffy brown with dark spots.  Surely not...?  Wow, that would be good!  I tried in vain to find images of this species' female genitalia.  Nothing online and the species didn't even feature in any of my books.  Externally the match wasn't perfect, which limited my rising excitement levels.  They look a bit like desertella really with smaller better defined dark spots.  This wasn't a good enough explanation to start asking experts to come up with images of their genitalia which would have had to have been my next step.

Eventually in the process of googling for plebejella I cam across a moth that looked more like mine than any others I'd found.  It was, or at least it was labelled, Bryotropha umbrosella.  The images I'd looked at were the dark form but it has a pale form too, and it looked very much like my moth!  That's it!  And it's preferred habitat is sand dunes, which is exactly right for where I found mine.  And there are records in NW Norfolk, so it all adds up!  Excellent, I thought, a new moth for me.  But was I sure?  The genitalia were close, but they weren't quite right.  Actually the closest thing to the genitalia was affinis, though it obviously wasn't that as they look nothing like my moth.

Reading the text about umbrosella in MOGBI there was a comparison made between the pale form of umbrosella and the pale form of affinis.  Pale form of affinis?  I didn't know there was such a thing!  I've seen loads of affinis and they've all been dark, and I've never seen a photo or any mention of a pale form before.  Can they really look like this?  Apparently they're rather like the pale form of umbrosella only the background colour is more buffy, less greyish-white.  Well the photo I'd seen of a pale umbrosella looked a bit buffy to me, but not so clearly so (and I'm only assuming it is correctly labelled).  I walked through the Bryotropha key in MOGBI carefully and sure enough it spat out my moth as affinis.  I walked it through the genitalia key too and yes, that confirmed it.  There were some differences between what I observed under the microscope and the diagrams of the genitalia, but in hindsight I think these can all be put down to minor variation and the fact that it was mashed about a bit during the dissection process.  After all this - and the whole thing probably took me 8-10 hours - it was just a Dark Groundling Bryotropha affinis!  But a fascinating individual of a form I didn't know existed and a great learning process.  Apparently the form occurs in coastal areas, which may explain why I've not seen it before - it's a species I catch commonly inland but the pale form wouldn't occur here.

Dark Groundling Bryotropha affinis (pale coastal form, female gen det), Burnham Overy, 8th June

Not many butterflies flying.  3 Brown Arguses were best, with Small Copper, Small Heath and Wall Brown also represented.  Among the other insects were three which I nearly identified as species that are new to me.  In each case I don't have quite enough information to be certain that other closely-related species are satisfactorily eliminated though.  One was this sawfly which I think is Allantus truncatus.  My new key only narrows it down to genus and although this species is common and seems to match my individual I don't have any information on how at least 2 of the other species in the genus differ.

probable Allantus truncatus, Burnham Overy, 8th June

Apparently 3 species of Sand Wasp occur in this locality - both the rather local Podalonia species and the more widespread Red-banded Sand Wasp Ammophila sabulosa.  I didn't retain a specimen but from my photos I think the degree of hairiness rules out Ammophila and probably favours Hairy Sand Wasp Podalonia hirsuta.  Not confident about that though, as I lack experience with these.

probable Hairy Sand Wasp Podalonia hirsuta, Burnham Overy, 8th June

This leafhopper seems to be a good match for Ribautiana debilis but I'm not sure if other members of the genus can safely be eliminated.

probable Ribautiana debilis, Burnham Overy, 8th June

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