Brief life of magical mayflies

LAST WEEK I was sitting in my canoe bailing out rain water when a large and beautiful insect floated by on the river --- a mayfly. 

The fact that it was nearly June and this was the first one I’d seen this year wasn’t really surprising. Mayflies can emerge at any time from April through to the autumn but the principal hatches are normally in late May and early June. The reason the name doesn’t coincide accurately with the month is because they were named before the Pope changed the calendar and at that time May was a couple of weeks later in the year.

The larvae of mayflies, which anglers call nymphs, live for two, occasionally three, years on the bottom of suitable lakes and rivers. There they burrow into silt or sand and filter organic matter out of the water. They grow continuously and this involves regular shedding of their external skeleton and producing a new and larger one. Biologists call each of these stages between moults an ‘instar’.