Last week (22 May 2018) on our walk around Stony Stratford Nature Reserve we saw lots of mayflies pulsating up and down above the river and settled in the foliage on the banks. On coming home I then read a very interesting article on mayflies by Nick baker in the BBC wildlife magazine and thought I would pass on some of the interesting facts here.
The mayfly we saw is I think the green drake or Ephemera danica which is the biggest of the British species, some of the other 51 species being absolutely tiny.
These mayflies, commonly copied by anglers for their lures, dance above the water in a mating frenzy with the females emitting an intoxicating perfume that attracts the males before she scatters her clutch of up to 8000 eggs into the waters to pass on her genes to the next generation. These eggs sink to the bottom and turn into nymphs which spend the next 1-3years developing in the sediment at the bottom of the river. Meanwhile their parents dancing above last but a day or two before they die (having no mouthparts they rely on the fat reserves laid down as a nymph to power them through this stage).
The nymphs carry on their lives in the river moulting up to 50 times before they are finally ready to return to the surface. At this stage they blow up like little air filled balloons and bob to the surface. Almost immediately on hitting the surface they unzip in a matter of seconds and emerge as adults with fully functioning wings. You might think this was their final moult but no they are unique in the insect world in having a second moult from one rather dull winged form to another, this time the sparkling beauty we saw last week. Why they do this no-one really knows.
Then the dancing begins and the whole lifecycle starts all over again.
One final fact – mayflies are the most primitive insects alive today and have been around since before the dinosaurs.
What an amazing insect!
Article kindly supplied by Julie Lane