Monday, December 17, 2007

Red Underwing Moth Catocala nupta

I am an amateur naturalist trying to find out what lives in my garden.

Photo 1 (click to enlarge) shows a large moth that I found powerfully fluttering its way around my garden one afternoon, late last summer. From R. Lewington's truly beautiful illustrations in my newly acquired copy of the Concise Guide to Moths of Great Britain and Ireland (Townsend, Waring, British Wildlife Publishing ) I'm confident to identify he (or she - can anyone comment?) as a Red Underwing (Catocala nupta).

The book lists eight species of Catocala moth, a number of which (the Red, French Red, Rosy, Light Crimson and Dark Crimson Underwing) are superficially rather similar.

The caterpillars of the Red Underwing feed on willow and poplar.

In Greek 'kato' means 'below' and 'kalos' 'beautiful' (see here for a detailed discussion) - hence Catocala - a genus of moths with 'beautiful hind wings'.

The species name nupta means 'a bride' and was coined by the father of modern taxonomy Carl Linnaeus. Linnaeus was apparently fond of giving this name to moths with bright underwings and in my copy of the fascinating Moths (Michael Majerus, New Naturalist series) A.M. Emmet is quoted as wondering whether brides in eighteenth-century Sweden were in the habit of wearing brightly coloured underwear!

The red underwings serve as a defense against predators. In his book Michael Majerus suggests two mechanisms: firstly, the flash of red and black from the underwings may serve to remind birds of unpleasant tasting insects such as wasps or ladybirds. Secondly, a predator with its mind focused on chasing a flying moth "with red wings" may lose track of its prey when the moth lands, closes its wings (photo 2), and instantly becomes a dull cryptic grey/brown well camouflaged against a tree branch.

Another interesting fact I discover from the book above is that Catocala nupta has been recorded as showing full industrial melanic polymorphism - or, in layman's terms, the advent of heavy industrialisation has caused the evolution of a subspecies of Red Underwing with darker wings designed to give the moth better camouflage against grimy, polluted surfaces (soot-stained tree trunks etc.). Strictly, I'm taking some licence in my explanation: in point-of-fact the book merely states that a melanic form of C. nupta exists without giving any details of its camouflage strategy. (The famous example of a melanic moth is the Peppared moth which has provided a vehicle for extensive studies of Darwin's theory of evolution - Majerus' devotes a an entire chapter to a fascinating account of these studies). I've searched the internet in vain for an image of a melanic Red Underwing (anyone?), although Townsend and Waring's book does contain a picture of a form ("f.") of the Red Underwing Catocala nupta f. brunnescens, which has dirty brown underwings. Can anyone tell me whether this is one-and-the-same as a melanic C.nupta?

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