The progress of Autumn was indicated last night by the species count dwindling to 14 and the two lights yielding just a single and very battered Square-spot Rustic. My run of Autumnal Rustics seems to have come to an end, but Lunar Underwing were still going strong with 139 individuals, including a few very smart examples.
Among the moths attracted to the actinic light was a Conistra (Chestnut) species, but which one?
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| Conistra sp., Newton Longville 27 September 2020 |
When I first saw it, I wondered if it might be Dark Chestnut (C. ligula). A closer look at the photograph has increased my uncertainty: the wingtips may not be sufficiently pointed, so is it a Chestnut (C. vaccinii)?
Website research has increased my confusion: the British Lepidoptera site mentions that the rare migrant Red-headed Chestnut (C. erythrocephala) has the head colour lighter than the thorax. While it's true that my two-tone example doesn't seem to be echoed in photographs of ligula or vaccinii, other aspects seem to rule out erythrocephala: the moth I caught was rather stubby and not large enough, also lacking the required black dots in the trailing edge of the kidney-mark. It is slightly darker there, which is more typical of vaccinii. It's also notable that the oval is squashed and slanted, something that isn't mentioned in any text that I've found, but which is seen in some photographs of vaccinii.
Overall, I'm leaning more to Chestnut (C. vaccinii), but help would be appreciated!
Newton Longville, Bucks
Hello Tim,
ReplyDeleteThat's a Chestnut (vaccinii). The colour and intensity of the markings on Chestnut and Dark Chestnut (ligula) vary considerably and there's a degree of overlap, so the best indicators are wing shape and whether the moth has an 'oily' appearance or not. When fresh, Dark Chestnut has a much straighter costa with an obvious sharp 90 degree angle between it and the termen, although of course the wing-tip is often the first area to suffer damage in worn examples! The overall shiny appearance tends to stay with the moth, though. A record of Red-headed Chestnut (erythrocephala) this far inland would be exceptional for such a rare species. It is larger than either of the others and has black dots around the edge of the kidney mark which are diagnostic.
Thanks for the explanation, Dave. The tips on Dark Chestnut are very helpful.
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