Scarce Maple Stilt Caloptilia hemidactylella

Until recently very rare in Britain and apparently thought to be unlikely to occur in Norfolk. That changed after three records in 2018-19 followed by 15 records in 2020. Formerly given the vernacular name Sycamore Slender

Several species look similar to hemidactylella, especially the new British species Caloptilia Caloptilia honoratella, which it seems is also colonising Norfolk. I don't know of any reliable means of separating these two species based on external characters, so recommend checking genitalia to be certain.

This one is the first I have caught. The cornuti in the aedeagus are distinctive, lacking in honoratella and different from those in e.g. falconipennella. The cornuti are in the vessica outside of the sclerotised section of the aedeagus so could be lost if insufficient care is taken with the dissection. Note the larger first cornutus with its dark tip one end and tapering tip the other end. The tip of the aedeagus is squared off, unlike the more pointed tip on honoratella.

male Scarce Maple Stilt Caloptilia hemidactylella showing genitalia including close-ups of cornuti and tip of aedeagus, near Gressenhall (Norfolk, UK), 18th April 2022

The next two were sent to me by Dave Jones who caught four similar-looking moths over a few days in his garden. Dave suspected hemidactylella was the ID but it seemed sensible to confirm, especially as some commentators suggested they might be something else (one experienced moth-recorder even felt one of them was likely to be falconipennella).

male Scarce Maple Stilt Caloptilia hemidactylella showing genitalia, Stoke Holy Cross (Norfolk, UK), 14th April 2022

male Scarce Maple Stilt Caloptilia hemidactylella, showing genitalia Stoke Holy Cross (Norfolk, UK), 14th April 2022