The Hawthorn fly
Photos and text from Chris Reeves
Bibio marci or St. Mark’s fly or more usually the hawthorn fly, is a species of fly from the family Bibionidae. It is found across much of Europe. Their name comes from the fact that the adults usually emerge around St Mark’s Day, 25 April.
The fly is terrestrial in that it doesn’t spend part of its life cycle in the rivers or ponds as do many insects relevant to trout fishing. It is when the flies fly to mate that they become of interest to the trout and the angler. They are rather large insects with a decidedly droopy look about them. The adults fly slowly and are easily knocked onto the water by anything more than a light breeze. In a good year, they are about in huge numbers and can cause massive rises on both rivers and still waters.
Dressing for the Hawthorn:-
Hook:- Size 10 Partridge PWW (Wide wet)
Thread:- Black 8/0 Uni or similar
Body:- Black Micro chenille singed at the end to form a taper.
Legs :- Two pairs of knotted black cock pheasant centre tail with the tips cut off
Wing:- 6 to 8 short strands of pearl or clear crystal flash
Hackle:- Ten turns of a good quality cock saddle hackle. (Whiting for preference)
Lay down a bed of thread and stop immediately above the hook point
Singe the end of a length of Micro chenille with a candle to form a point and tie in a body projecting 2cm behind the tie in point.
Tie in two pairs of single knotted cock pheasant centre tail on each side of the hook, with the legs projecting downwards. Cut of the tips
Tie in a small bunch of Crystal flash on top of the body to form a wing.
Tie in and wrap the hackle. I like to use a good long saddle feather and get at least 10 turns of hackle. Don’t crowd the eye.
Whip finish and varnish the head.
How to fish the Hawthorn.
This is a fly that not only works when the real insect is on the water but can also fool fish into rising when there is no natural about due to its size and busy profile.
I like to fish it singly on rivers but will use it as one of a two fly cast on reservoirs, It’s size and colour make it easy to see and an ideal fly to fish in conjunction with a smaller dry that represents a water bred insect.
I was fishing the Delaware River, the evening of May 2, 2024 on a riffle close to the Pennsylvania bank. Trout were rising feverishly here but not so much out in the adjacent pool. I tried a couple of emergers to no avail and a relatively large, black fly landed on my vest. It looked like a flying ant (my first reaction). But these normally mate in the US in late August or September. Anyway, I put on the right size ant, a #12, and took a fat 16″ rainbow on the first cast. But I couldn’t interest the others and the action soon stopped.
I couldn’t identify this insect, but was aware of something similar when I have fished the UK and Ireland; if right, it is a significant fly. The following day, sitting on the bank one landed and I got a closer look at this fly and made notes to describe it. I felt like I was onto what may be a rare occurrence – at list in 50 years of fishing the Catskills I had never run into the Hawthorn fly (genus Bibio) but I am certain that’s what it was. – a long thin black abdomen, a heavy black thorax, clear wings the length of the abdomen and folded flat like a stonefly’s, and maybe six black legs. Could it be native or an invasive species? I have never read of Bibio in any North American fly fishing literature which is pretty extensive. Any thoughts?