Spiny Hook-tip confirmed (and a thorny problem)

David Carter caught a male hook-tip in Windsor (Berkshire) on 8 November 2024. From the appearance and the late date Dave thought this was a candidate for Spiny Hook-tip, and it has now been confirmed following Peter Hall's dissection.

Congratulations to Dave on a new macro-moth species for the county (and the first confirmed record for Upper Thames as a whole as far as I'm aware). Elsewhere Spiny Hook-tip seems to be established in an fairly large area around Bristol and nearby parts of South Wales, since 2023 and maybe earlier, based on gen. det. records; confirmed or suspected records are now accumulating in a number of other English counties. The caterpillars feed on Holm Oak, but may also use other oaks and possibly birches.

The thorny problem is that Spiny Hook-tip is very similar to Oak Hook-tip, and as yet it is not clear to what extent the markings and colours overlap between the two species. Clues for Spiny Hook-tip seem to be focused mostly on the wing apex, where the black markings and contrasting pale patches often have a slightly different shape in the two species. Some individuals of Spiny also have a darker greyish tint over the wing as a whole. But the markings seem to vary between individuals, and it is not clear to me whether the distinguishing features are consistent throughout the year. And of course worn specimens will pose further problems. Further work is needed to clarify the extent to which the two species can be distinguished by sight.

The dissection for Dave's moth can be seen on the Moth Dissection website. See also a discussion on BirdForum about the records from other counties and some of the potential distinguishing features.

Spiny Hook-tip, Windsor, 8 November 2024, recorded and photographed by Dave Carter