Dusky Ridge-back Phaulernis dentella

A day-flying moth that is typically found round umbellifers. Formerly given the vernacular name Scale-tooth Lance-wing.

My first was a nice fresh individual and straightforward to identify.

Dusky Ridge-back Phaulernis dentella, North Elmham Cathedral Meadows (Norfolk, UK), 6th June 2018

The next one was netted in exactly the same place just over a year later. The shape reminded me of the above specimen but it was much more worn making it difficult to see enough detail to confirm the identification. To make certain I dissected it, but this did not provide immediate confirmation. The problem was I couldn't find any description or image of female dentella genitalia anywhere in any of my references or on the internet. The genitalia were similar, but not identical, to the image of female Yellow-spotted Drab Phaulernis fulviguttella genitalia at the Moth Dissection website. The differences were probably significant enough to rule that out, but I wasn't completely certain about that. The genitalia of some of the Epermenia species were rather similar too, and images were missing for one or two species. In the absence of being able to make a certain ID from external characters and in the absence of any information about what the female genitalia of dentella should look like I pended the record.

Four years later I finally netted another and although the ID was clear from external characters, I retained it in the hope that it would be a female and help me to clear up this record. In the meantime an image of female dentella genitalia has now been added to the Moth Dissection website. I was at last able to confirm this record from 2019.

female Dusky Ridge-back Phaulernis dentella showing genitalia, North Elmham Cathedral Meadows (Norfolk, UK), 21st June 2019

This was the one I used to help confirm the above worn individual. Based on a comparison of two images of female fulviguttella genitalia (one at the Moth Dissection website and one at Lepiforum) and two female dentella (the one image now at the Moth Dissection website and this individual) I think there are two key differences. Firstly the signa in both species consists of a paler central area separated by a thin dark border from the darker outer part (sides and round the bottom). On both images of fulviguttella the pale central area and its border is sharply pointed as a narrow V whereas in the image of dentella and this individual, it is broader and more U-shaped. Secondly near the top of the ductus bursae there is a slightly swollen region that is clearly spiculated on dentella and has a clear diverticulum, similarly spiculated, emerging from the side. There is a lightly sclerotised band above this at the top of the ductus bursae. So far as I can see in the images of fulviguttella neither the bulge, the divericulum, the spiculation nor the sclerotised base are present on fulviguttella - however the photos do not show this region very clearly so I would like to see better images of fulviguttella to be clear how much this significance to attach to this apparent difference.

female Dusky Ridge-back Phaulernis dentella showing genitalia, Wendling Beck Environment Project (Norfolk, UK), 15th June 2023