Hunting for Bibionidae

One of my goals for this year was to search for specific insects that I have blogged about or would like to write about and take my own photos for the articles. One of the early season target species was Bibio marci, known commonly as the St Marks fly or the hawthorn fly, which is on the wing in April and May. The COVID19 lock-down has limited my hunting ground somewhat to the hedgerow and woodland margins within a few minutes walk from the house during our exercise hour.

I have been keeping an eye out when we walk for the target species although I was not super hopeful that I would encounter them just around the corner. So imagine my surprise when I noted some bibionidae on the footpath right next to some newly emerging spring wheat less than 10 minutes walk away from the house. The males were hovering about half a metre off of the ground in a small swarm of 10-20 individuals. While it was very windy which made taking a photo with my mobile phone in the swirling dust of such small flies tricky it might also have been a blessing as they needed to escape the wind and take a rest on the grass and the footpath itself. 

Closer inspection of the photos revealed that the species was Bibio johannis characterised by their pale orange legs amongst other attributes. Bibio lanigerus occupies similar habitats and is distinguishable from B. johannis by its darker fumose wings. I had researched and was well aware of the hawthorn fly as well as the heather fly (Bibio pomonae) but paid little heed to the other bibionidae. The fact that both B. johannis and lanigerus also have reddish orange legs which would likely act as a trigger for hungry trout in a fly pattern reinforced why the pattern is so successful. This got me wondering what other bibionidae one might encounter and if they also have reddish triggers. Bibio marci, pomonae, johannis and lanigerus are the most common species you might encounter. In additon, B. nigriventris also has orangey legs.

So that got me wondering if Bibio marcii also might be present locally and have been keeping an eye open for it. On the 24th I spotted a small swarm along a hedge line adjacent to the local football pitches but as luck would have it they were all hovering about 4m off the ground and out of capture and photographing range. I returned the next day and they were nowhere to be seen but encountered a much larger swarm on the other side of the park along the edge of a small woodland. I managed to photograph a few large males and was quite chuffed, photographing a St Marks fly on St Marks day. Since then I have encountered them in multiple places and got some amazing photographs of them swarming and resting on some bramble. A week later I encountered another smaller species of the Bibionidae in a similar location with black legs and dark fumose wings (Dilophus febrilus?) 

Tight Lines

Greg