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  • Writer's pictureWildlife Friendly Otley

st mark's fly

ST MARK’S FLY: This is that shiny black fly with the dangly legs that you see in swarms at this time of year. Some people find them annoying, but they are an important pollinator (feeding on nectar). The name derives from the fact that most adults emerge around St Mark’s Day – the 25th April. Another name is Hawthorn Fly. Numbers peak in May, but they’re still around now. The males have the long legs, but the females are larger overall. The males’ eyes are larger, too, and have separate connections to the brain. This allows the males to use the upper eye part to look out for females and the lower part to monitor their position in relation to the ground, allowing them to hover in the same position. St Mark’s Fly is another insect with a relatively short adult stage – about a week.

By Neil Griffin Photo by Anne Riley


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