Wondering if there are several species of Bibio called St Mark's Fly, or is there just B.marci?
No interactions present.
There are indeed several species of Bibio flying in Spring...often more than one species at the same time. marci is large and this does seem to be that species, as the legs are all black and there appears to be a dark costal area on the wings.
Really, though, with Bibio you need a photo from above, to see the venation properly, as well as a shot of the spurs on the front tibiae. Some of the smaller species are hard to tell apart from a photo.
Have a look at Steven Falk's excellent pictures...
My Flickr photos...
The confusion sp. seems to be B.leucopterus. I have posted a poor shot of the wings which just abut shows a darker costal region. The main pic does show a spur on the front tibia. The fact that you can't see two suggests that any other one is much smaller, which also points to marci.
I must look for some others next spring, with my new macro attachment!.
Jamie from Briantspuddle
One of them is usually hidden in a photo, unless you get it from exactly the right angle, so you can't read too much into the size of the second one, here. This is marci, though, I agree, as the dark costal area is clearly there.
Not long til they are out again...and they are very common flies in early spring.
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