Oops, got that one wrong


Flanders Moss NNR

On Sunday I blogged about a huge fly I saw on Flanders. In the post here I said that it was a Noon Fly which has a fascinating lifestyle of moving between cowpats and flowers. Well though I had got a confirmation of the ID it turns out we were wrong. Sorry. Fake news.

In fact the fly was a Giant Tachinid Fly (Tachina grossa. )  This is actually one of the largest flies in the UK, (I said it was big) and has a huge swollen body covered in big bristles with yellow ones around its face and neck. It was described to me as the “orange-faced Donald Trump fly” but I couldn’t possibly comment on the likeness.


Like the Noon Fly the adults of these species feed on nectar and pollen on flowers. But the larva live in live caterpillars. Yes, live caterpillars. The females lay their eggs on the big hairy caterpillars found across Flanders, like those of the moths northern eggar and fox moth. The larva hatch out and live in the still alive caterpillar basically eating it from the inside out and eventually killing it. When you think about it this is a delicate operation as they don’t want to kill the caterpillar too quickly so they have to munch at just the right rate that means that caterpillar dies when the larva are nearly mature. And if the caterpillar is weakened too much it can easily become prey to the cuckoos, larva and all. So there is more to this “Alien” lifestyle than you might think.

Anyway apologies for the fake news, will try to get it right in the future.

This is a Noon Fly, much smaller, less bristles and no orange facial bristles.


noon fly


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