Hi Nic, the white specks seem to vary in brightness in both species, although as might be expected they may sometimes stand out more on the Dark Chestnut. While it can be difficult to determine, the most important criterion to separate these species is the straightness of the outer wing edge (termen) and consequently the 'pointedness' of the wing tip (apex). If the outer edge of the wing (termen) is curved (convex) so that apex looks rounded it is a Chestnut - but if the termen is straight (at least over the region close to the apex) or concave so that the apex is at a right angle or projecting it is a Dark Chestnut. Dave put a picture of the two side-by-side in a previous post: https://upperthamesmoths.blogspot.com/2019/10/westcott-bucks_11.html and gave further advice on this question. To me, as you suggest, your moth probably qualifies as a Chestnut.
Hi Nic, the white specks seem to vary in brightness in both species, although as might be expected they may sometimes stand out more on the Dark Chestnut. While it can be difficult to determine, the most important criterion to separate these species is the straightness of the outer wing edge (termen) and consequently the 'pointedness' of the wing tip (apex). If the outer edge of the wing (termen) is curved (convex) so that apex looks rounded it is a Chestnut - but if the termen is straight (at least over the region close to the apex) or concave so that the apex is at a right angle or projecting it is a Dark Chestnut. Dave put a picture of the two side-by-side in a previous post: https://upperthamesmoths.blogspot.com/2019/10/westcott-bucks_11.html
ReplyDeleteand gave further advice on this question. To me, as you suggest, your moth probably qualifies as a Chestnut.
Really appreciate the comprehensive reply John. Clearly a very tricky species pair!
ReplyDeleteRegards,
Nic.