Coast Straw Gynnidomorpha permixtana

Formerly given the vernacular name Coast Conch.

The following moth turned up in Garry Barlow's trap during a Norfolk Moth Survey event. It was passed round everyone present and no-one could name it for sure but, after a quick look at some photos on my phone, I suggested it might be Gynnidomorpha permixtana. On the face of it that seemed very unliklely as there were no Norfolk records (or, as it turned out, from Suffolk or Essex - a 19th century record from Cambridgeshire appears to be the only East Anglian record). On further investigation the genitalia seemed to fit permixtana. I was hesitant about this ID because I couldn't find any photos of male Fen Straw Gynnidomorpha minimana genitalia which sounded like they should be quite similar from the descriptions. The photos of minimana moths I’d seen didn’t look much like this moth so I did’t think it can be that, but perhaps it was more variable than is suggested by the few images I’d seen? I thought Saltern Straw Gynnidomorpha vectisana could look quite similar externally but if I’d understood the differences in the genitalia correctly it couldn’t be that. The socii looked very much like the photos on the Moth Dissection website for permixtana.

Given its rarity I felt that it would be prudent to get a second opinion and contacted Jon Clifton. He in turn contacted Bob Heckford who has reared these from larvae and published a paper* about them which he forwarded to us. Bob noted that it looked more orange in my photos than the examples he had come across (I think my photos may have exaggerated this slightly) but supported the ID.

Bob asked about the presence of Yellow Rattle or Red Bartsia at the site as, although other foodplants are listed historically for this species, these are the plants where he has found the larvae. There was a considerable amount of Red Bartsia growing at the site.

* S D Beavan and R J Heckford (2012). Discovery of the larva of Gynnidomorpha permixtana ([Denis & Schiffermüller], 1775) (Lepidoptera: Tortricidae) in the British Isles and a consideration of the species’ distribution. Entomologist’s Gazette 63: 69–83.

male Coast Straw Gynnidomorpha permixtana showing genitalia, Brickyard Fen, Surlingham (Norfolk, UK), 26th August 2017

Laura King trapped the following moth in her Lower Hellesdon garden. She sent me photos, unsure of its identity, and we soon figured out that it was one of the Gynnidomorpha. Based on her initial photos I wondered if it might be minimana which would be an excellent record, but advised that it should be gen detted to confirm and collected the moth on my way past the next day. Examining the moth I became less convinced that it was minimana and wondered if permixtana might be the answer, given the presence of some dark grey speckling in the outer part of the wing. At this point I was not 100% sure I could eliminate vectisana either, or possibly Water-plantain Straw alismana. Photos of the non-Norfolk Bartsia Straw luridana looked rather more obviously different, but I figured I should consider this too when examining the genitalia. There was a niggling doubt in my mind that I'd overlooked something entirely different - after all the ObsIdentify app was 98-99% certain that my photos showed Agrimony Straw Cochylidia rupicola...

It was a female, and the genitalia did indeed resemble those of Gynnidomorpha species - and not Cochylidia rupicola! All the photos of female luridana genitalia on the Moth Dissection website and Lepiforum and the figure in MOGBI show an appendage to one side of the ductus bursae, lacking on this moth - so that was eliminated. Judging from the figures in MOGBI and the photos on the Moth Dissection, Lepiforum and British Lepidoptera websites, it looks like the corpus bursae is narrower on vectisana and alismana, compared to permixtana and minimana. For the moth in question, the corpus bursae broadens out substantially so seems closer to permixtana and minimana in that respect, but there is variation on all depending on how the genitalia are set. Another apparent difference between the two pairs of species is what I think is the edge of segment 8 - in effect the line of the apophyses anteriores turns sharply to run flat towards the centre across the distal border of segment 8 and then sharply again to run a short way down the inner edges where segment 8 is presumably split - the corners being square so effectively making a nn shape. It's a little hard to be sure as it depends how the genitalia are positioned, but this seems to match permixtana and possibly minimana whereas the angles seem less sharp on vectisana and alismana and they don't appear to have the lines extending down at the centre. At the inner corners of the nn lines, there are 2-3 prominent hairs and some dense horizontal lines of light spiculation. This is matched by photos of permixtana genitalia but there is no sign of it on any images I've found of vectisana or alismana, so I think all this adds up to enough evidence to rule out vestisana and alsimana.

Eliminating minimana is harder. I have only found one photo of female minimana genitalia (on Moth Dissection - it's not a particularly clear photo) and the rather tiny diagrams in MOGBI. It looks like the inner edges of the nn shape described above are less distinct and more curved, the corners being less square and the inner lines continuing to curve back towards the outer edge. The gap is shown as wider, but that might just be the positioning, and it doesn't look like the hairs and lines of spiculation at the corners are so prominent/extensive. It looks like there's a difference in the size and position of the horseshoe-shaped spiculate signa in the corpus bursae - smaller, nearer the top and taking up around a third of the height of the corpus bursae in minimana, larger and extending further down in permixtana. This horseshoe isn't easily seen in my photos as the corpus bursae wasn't well cleared, but it is more extensive and covers at least half the height of the corpus bursae. A possible further difference lies in the shape of the sterigma (if I've identified the part correctly - the roughly rectangular-shaped band at the top of the ductus bursae). Judging from the diagrams in MOGBI it is narrower in permixtana (roughly 2.8 x wider than high - measured centrally) than in minimana (2.4 x wider than high). I'm not entirely clear if this is supported by all of the photos, but on Laura's moth it is narrow, 2.9 x wider than high.

All things considered, I am, a little tentatively, identifying Laura's moth as Gynnidomorpha permixtana, the second for Norfolk. Of course I welcome feedback on this identification. I am glad I took some photos of the genitalia before setting it as placing the cover slip skewed it somewhat so some of the characters described above are no longer clear.

For the Brickyard Fen moth, Red Bartsia was the probable foodplant but here it may have been Yellow Rattle. Laura has had Yellow Rattle growing in her garden this year, and her next-door neighbour has had it for a few years.

female Coast Straw Gynnidomorpha permixtana showing genitalia, Lower Hellesdon (Norfolk, UK), 30th July 2022 (trapped by Laura King)

If there was an iota of doubt about Laura's female, then this was cleared up the following year when Laura caught two more - both males. It seems that her crop of Yellow Rattle is coming up trumps! Once again the ObsIdentify app thought this one was Cochylidia rupicola but Laura was rightly sceptical about this ID and checked it with me. We suspected it was another Gynnidomorpha permixtana and upon dissection this proved to be the case. The narrow socii (abruptly narrowing half way along) seem to rule out most Gynnidomorpha species but this feature is shared by minimana. However minimana has a much longer cornutus in the aedeagus. The first two photos below were taken by Laura.

male Coast Straw Gynnidomorpha permixtana showing genitalia, Lower Hellesdon (Norfolk, UK), 28th July 2023 (trapped by Laura King and photos of live insect are by Laura)

Again the first photos below was taken by Laura.

male Coast Straw Gynnidomorpha permixtana showing genitalia, Lower Hellesdon (Norfolk, UK), 18th August 2023 (trapped by Laura King and photo of live insect is by Laura)