Hawthorn Fly

The Hawthorn fly (Bibio Marci) is one of the first flies of the season known as 'Terrestrials', these are flies which do not originate from the river, but do end up on it as food for Trout. The Hawthorn Fly is sometimes known around the country as The St. Mark’s Fly, because they emerge around St Mark’s Day (25th April) every year. This fly belongs to the Family Bibionidae and there are around 20 different species found throughout the UK.

Where To Find Them

Hawthorn flies are found in every part of the British Isles, especially prolific in England, Wales and Ireland. Scotland does have prolific hatches of Heather flies (Bibio pomonae) which are very similar to Hawthorn flies and are discussed below.

Hawthorn flies are found around woodland edges, hedges, and wetlands and can be seen in the UK throughout spring.  


When To Find Them

Hawthorn flies generally start to appear around the 25th April (St Marks day), when they do start to hatch they can be very prolific and you will see clouds of them. They usually only appear in any numbers for a short time and usually into the second week of May, they are gone.

What To Look For

Male Hawthorn flies are around 12mm (size 14 to 12 hook) in length with clear wings, large eyes and long gangly legs (this is the bit we believe the trout home in on - most imitative Hawthorn patterns you see generally extend the length of these rear legs). The females are slightly larger than the males (at around 14mm - a size 12 hook) with slightly smokey-brown coloured wings. You will often see male Hawthorn flies congregating in large swarms flying slowly, up and down, at around head height – trying to attract females.

The Heather Fly (Bibio pomonae) is more prolific in Scotland than the Hawthorn fly, but as far as fly anglers are concerned these species can be lumped together. However, the Heather fly hatches at a different time of year to the Hawthorn Fly, usually from July to September. The Heather fly can be easily identified by its red thighs (see below).


The Hawthorn Fly has a very short life cycle, hatching and being in flight for only around a week. They start life larva in the soil, this can be for up to 6 months.

During autumn and winter, the Hawthorn fly larvae feed on rotting vegetation. In springtime, the males emerge first followed by the females a few days later. After mating, females lay their eggs in the soil and die soon afterwards and the cycle continues.

Swarms of Hawthorn flies flies may be very annoying when fishing in the early spring, but they are very useful creatures, they feed on nectar, making them important pollinators of fruit trees and crops.

From a fly fishing perspective there is only one stage which we must try to imitate:

  • Adult


The Hawthorn fly can also be used as a suggestive pattern for a number of different insects, it can imitate a Heather Fly, Daddy Long Legs/Crane Fly and even an adult buzzer. Once the Hawthorn hatch starts on your local river, make sure you have these in your fly box these are also great flies to try when searching stillwaters & reservoirs.


The legs on these flies seem to act as a trigger to the fish. These flies are tied on size 12 and 14 barbless hooks with a bushy hackle, this allows them to create a wake on the surface when retrieved on stillwaters, again another trigger point the fish home into. These flies are also surprisingly effective when fished as a wet fly, so don't be too quick to keep these flies dry, once wet and submerged, if on a stillwater, gently "figure of 8" them back (on a river try fishing them as you would a spider), and hold on!

Top Tip: Fish these flies in the surface film, do not apply any floatant on them.

Hawthorn Fly

 Hawthorn CdC

Hawthorn Suspender


This email is brought to you with the sole intent to spread the information around so we can all maybe learn something. If you would like to buy any of the flies contained within this email, we do hope that you will consider us and see what flies we have to offer. If you would like any further details on any of the above flies, they can be found using these links:

Adult Fly:
Hawthorn Fly
CdC Hawthorn Fly
Hawthorn Suspender

Previous issues of Hatch Chat can be found on our Hatch Chat blog, here: https://www.barbless-flies.co.uk/blogs/hatch-chat