The Hawthorn fly is identified by its black trailing legs when flying. It hatches around the time of the Hawthorn bush flowering (mid-April to mid-May) and swarms of flies hover around the bushes and occasionally down to the water, where they are hungrily devoured by trout. If you look closely at the the bush, you will see many Hawthorn flies sitting on the leaves.
The fly has a black body and black wings. When on the water, its legs become an attractive trigger for the fish.
This variant of the pattern has a black body and small black hackle with long brown trailing legs and a red tag.