March Brown Frenzy

 

We had an unusual visitor a few days ago. The March Brown Mayfly (Photo 1).

Photo 1: March Brown Mayfly on Kitchen Window (19/3/26)

Why was it an unexpected visitor? Well, it would have emerged from a river (presumably the River Wye, though possibly the Yazor Brook) and flown at least a kilometre in order to reach our house. The video below shows a March Brown emerging from the water and transforming into a mayfly.

Video 1: March Brown Mayfly From Water to Air

The March Brown is also unusual in that it has only two cerci (tails) whereas most mayflies have three. This makes identification a little easier when they are spotted in March/April.

In one of those strange coincidences that happen from time to time, I had just been reading about the March Brown in a newsletter from the Wye and Usk Foundation (WUF). Excerpt below: 

Usk March Brown

After a long, wet winter, our rivers are flowing strongly. The spring sunshine finally has some warmth. The daffs are waving in the breeze and the lambs are frolicking in the fields. For the Usk trout fisherman this means one thing…. March Browns. The first reports came in over the weekend of trout going crazy as these large flies exploded from the surface.

 

One minute you are basking in the mid-day sunshine, then you notice the wagtail waiting expectantly on the bank to dash across the river. This is the cue to get ready. Within a few seconds the river explodes into life. Big brown flies burst from the surface and, seemingly, every trout in the river slashes and surges to make the most of the sudden feast. Within a few minutes it is all over. If you are unlucky that’s your lot and it is back to the nymph rod, but more often you get multiple waves and, as you move to month end, it becomes sustained. Often the frenzy turns into more leisured munching as the large dark olives take over.

Our March Brown specimen must have avoided being eaten before making its way to our house. This mayfly emerges from the water during the warmest part of the day (i.e. 11 am to 4 pm). Photo 1 was taken at 3 pm so either the March Brown was lucky or its survival says something about the decline in the trout population in the River Wye.

The March Brown is probably the best-known of the British mayflies because of its use in fly fishing when fishing for trout in March and April.

 

Photo 2: March Brown Mayfly (19/3/26)