Monday, 8 June 2009

Banded Demoiselles

Out walking in the valley earlier this week I was cheered to see an insect I always associate with those first really warm days of the year: the banded demoiselle (Calopteryx splendens). Banded demoiselles are damselflies, smaller and more slender than their robust cousins dragonflies and hawkers, but one of the first of this group of insects to be seen each year. The clue to identifying them is in the name as banded demoiselles are easily identified by a dark blue thumbprint shaped band on otherwise translucent wings which in flight gives the impression of an almost butterfly like flitting flight.

Banded demoiselles emerge in mid May and can continue through to September although in the Mersey Valley I only ever seem to see them in May and June. Perhaps due to the relentless mowing of the river banks. What I always find fascinating about damselflies and dragonflies is that they only emerge as adults for a relatively short period of their life cycle. If you see damselflies flying around bonded together it is because they are mating. Once mated the male stays attached to the female until she has deposited her eggs by dipping her abdomen into the water and attaching the eggs to vegetation in the river. The eggs hatch after a few weeks, but it is then the larval stage which can last several years. Banded demoiselle larvae live in muddy bottomed rivers and canals for 2 years until they crawl out of the water and across ground, up to 100m, to scrub or woodland habitat where upon the adult will emerge from the larval case.

My book tells me that "this species is very sensitive to pollution and needs healthy emergent plants for perches and egg-laying" so I'm interested to know from people who have lived near the valley longer than I have when banded demoiselles first became one of the wildlife stars of Mersey Valley.1

Richard Gardner, June 2009

1 Brooks, S. 2005. Field Guide to the Dragonflies and Damselflies of Great Britain and Ireland. Gillingham: British Wildlife Publishing.

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