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Monday, 5 July 2010

Burnished Brass split?

There has been a lot of speculation recently about the status of Burnished Brass moths in Britain, following a presentation by Colin Plant at last Novembers Annual Exhibition of Entomological and Natural History Society. He provided compelling evidence that the Burnished Brass should be split into two species, something the Europeans have been doing for some time. He suggested they could be identified on external features, the difference being the 'bridge' between the two gold bands on the forewing. If the bands were joined it was the new species Cryptic Burnished Brass Diachrysia stenochrysitis (sic), and if not linked was the 'old' species of Burnished Brass Diachrysia chrysitis. Both forms are illustrated in Waring and Townsend.

I add the following information from Charlie Fletcher:

"It is almost 50 years since the suggestion was first made that an additional species may be present within the taxon Diachrysia chrysitis.  More recently is has been shown that the moth that had been referred to in Europe as ssp tutti is in fact a sibling species of D. chrysitis, the western representative of the eastern species D. stenochyrsis. The English name Cryptic Brass has been suggested for this species. Following a long investigation, the two species have been definitively distinguished by their morphology, differences in structure of the wings scales, electrophoresis and different male pheromones.  So far as it is known, the two species have a similar distribution in Europe, including Britain"

"In the field, separation is based on whether the brown, non-metallic median fascia is complete (chrysitis) or interrupted by a band of green scales, these thus forming an "H" shape (stenochrysis). Examples at each end of the spectrum may be safely named using this character, however intermediate examples exist where the median fascia is traversed by a very narrow line of green scales.  These will probably require examination of genitalic characters to be certain of the species. However a character that appears to be fairly constant is that in
stenochrysis, the upper end of the lower section of the brown median fascia is distinctly rounded. In specimens of chrysitis where the median fascia is interrupted by a narrow line of green scales, this lower section tends to be square-ended."

Of course, this prompted me to look back through any photos I had, and of three that I found, there were examples of both species and an intermediate.

Windmill Farm, Cornwall, 12 Sep 2005

Lyons Gate, Dorset, 12 Jul 2004

Lyons Gate, Dorset, 19 Jun 2004

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