Nature Notes #37
Whilst I was looking for something of interest on the umbellifer plants, I got attacked by a ‘Horse-fly’! It’s a summer hazard in grassy areas and Frodsham Marsh is one of their favourite hunting grounds. You have to run the gauntlet from the moment you emege from your car. I was parked at the old birdlog by No.1 tank but they appear from anywhere particularly by No.6 tank. They are more than a nuisance and inflict a nasty bite which can swell up in no time (especially if you are susceptible). I took the opportunity to turn the tables and potted one for further inspection. I wanted to know if they were indeed Horse-flies or a familiar looking fly? Apart from them being quite a complex-patterned fly, their eyes are amazing, reflecting the light in a sixties-style psychedelic pattern. They look really, really weird!.
Similar to mosquitos and other flying biters, it is only the female that inflicts the bite as she collects blood to use in developing her egg process. An anti-coagulant is injected and then the insect sits there drinking your blood. Yummy for her but not so favourable for her victim.
Worldwide there are around 557 species of Horsefly-type flies. Those found on the marsh are Clegs, rather than Horse or Deer Flies. Deer Flies are easily told by their spotted eyes and patterned wings and abdomens, so my insect a Cleg. Additionally, The Cleg fly is separated from a Horse-fly by how they hold their wings. Horse-flies hold their wings flat like typical flies. Clegs hold their wings roof-like over their abdomens at rest. ‘The males can be told from females by their eyes touching, the female eyes are separated by a gap. The above images show a female.
The commonest species is the Notch-horned Cleg, Haematopota pluvialis and as far as I can tell, that’s what the photos show. Others illustrated by Steven Falk on his Flicker stream are Long-horned Cleg, Big-spotted Cleg, Levels Cleg and Black-horned Cleg. Conceivably some of these could occur on the marsh as well.
Written and images by Tony Broome.