Mayflies in Dutch are called "One Day Flies". The adults live for a short period of time only: they mate, the female deposits her eggs in the water and they die. Adults do not even eat or drink during their short life. May-flies are very primitive insects that have been flying around for millions and millions of years. Attached to the backside of their bodies are always two or three very long hairs or wires. The larvae, called nymphs, live in water. All species look alike and it is almost impossible to distinguish between them when you're not an expert. So I did consult experts to help me with identifying the species below and this is what they answered: 'the species on the fotos is Cloeon dipterum (L.), a female, very common throughout Europe and very typical for smaller standing waters, as garden ponds. Biology is interesting as being ovoviviparous (as some nearctic Callibaetis). Females come into the houses for several days, to leave it after moulting, leaving their subimaginal skin at the house walls.' Now I must admit I had to look up the word ovoviviparous. I remembered the word from my schooldays, but I didn't remember the exact meaning of this difficult word. It means that normal insect eggs are produced, but not deposited. The eggs are kept inside the body, also during hatching. The young then leave the body of the mother alive. There are not many animals that do the trick. Some spiders and sharks give birth that way. Mr. Haybach then continues his identification with a subject for a typical scientifc dispute. 'There is a little problem, not with the taxonomy, but with the systematicsof this species. Some european workers as Eva Engblom, R. Sowa and me think that there are three species within a closely related group. (C. dipterum, C.cognatum, C. inscriptum) while the majority of european workers regard those as synonyms to C. dipterum."
We had quite some pictures of may flies on our site, wondering whatever species they could represent. Craig Macadam provided us with the answer: all belong to the same Cloeon dipterum group and all are very likely to be Cloeon cognatum!
In the top pictures you see the colourful female. In the bottom pictures the much darker, big-eyed male.