Tuesday, 18 June 2013

A spectacular cranefly and a deadly fungus

When I collected the catch of flies from the moth traps at Pitsford last week, Mischa Furfaro, one of the wardens on the reserve, gave me an unusual-looking cranefly that she had found on a tree trunk whilst checking the nest boxes. The cranefly turned out to be Ctenophora pectinicornis. This species is one of three British species of cranefly that mimic large ichneumons or wood wasps. They are all rather scarce. Apart from their smart black and yellow colouration, the males are distinctive because of their peculiar pectinate antennae, as can be seen in the photo below.

These craneflies breed in dead wood, typically high in trees and so tend to be associated with ancient woodland. The male that Mischa found may well have been searching for a female around the nest box.

On Sunday I visited a local wood and swept the fly shown below from the ride-side vegetation. It was dead and furry-looking growth was coming out from around the abdominal segments. This fly had been infected by an entomopathogenic fungus. There are several species of fungus that kill flies and other insects. Typically a spore is picked up on the surface of the insect. The spore then develops hyphal threads which eventually penetrate the insect's exoskeleton and continue to develop inside the insect. Toxins released by the fungus kill the insect. The fungus then produces its fruiting bodies on the outer surface of the insect and the next generation's spores are released. It normally requires conditions of high humidity for this cycle to complete. There is currently scientific research being undertaken to see if this could be developed as a biological control for certain pest fly species, including mosquitoes.

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