Friday, 21 March 2008

Hark the Herald...Moth

Visits to bat hibernacula sometimes produce sightings of other species, which also choose to hibernate in caves and mines. Mosquitoes and bees are occasionally found, but the ever-present companion of the hibernating bat is the Herald Moth (Scoliopteryx libatrix). I don't think I can remember every going into a hibernaculum without also finding Herald Moths: sometimes many dozens, often just one or two.



According to Butterfly Conservation, the organisation charged with conserving our diverse butterflies and moths, there are over 2,500 species of moth in the UK. So why the Herald should be the only one that seems to choose to overwinter in cavses and mines isn't clear. Many species spend the winters as eggs or as pupae, but quite a number apparently do overwinter as adults.

The Herald is a rather attractive animal, with wavy-edged wings coloured with reds and browns, which help it to blend in with dead leaves and avoid predators.

An interesting coincidence is that the Herald is a member of the Noctuidae family of night-flying moths. Something which sets them apart from other moth families is that they have developed a rudimentary hearing organ, which is used to detect the echolocation calls of approaching bats. On hearing an approaching bat the moths wings go into spasm, causing erratic flight, so that the moth is able to evade the bat.

The bats have the last laugh however, in the form of the Long-eared Bats (Plecotus spp.). which have evolved to get by with a very faint echolocation call. Their slow flying speed means that they have less need than other species for advanced warning of obstacles and their phenomenal hearing allows them to listen for prey. Their very faint call (they are known as the Whispering Bat) means that moths aren't able to hear them coming. Thus, a commonly-found sign of Brown Long-eared activity is a pile of discarded moth wings.

It is quite usual to see hibernating bats covered with droplets of condensation. What sparked off this foray into lepidoptery was the discovery today of a Herald in the same state, with huge droplets of water on it's antennae, creating the impression of some kind of miniature bog-eyed monster. Maybe this is the first sign of the moths evolving some form of revenge on the Long-eareds...


For more information on Butterfly Conservation go to http://www.butterfly-conservation.org

Another good source of information on moths: http://ukmoths.org.uk

My website: www.plecotus.co.uk

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