Mayfly (Heptageniidae)

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What funny little critters that the mayflies. They are said to have such a limited life expectancy that they will only see in their skinny existence one sunrise and one sunset… if they are fortunate enough to survive the countless dangers that are constantly waiting for them. Frail and fragile, with their big globulous eyes and wings awkwardly standing above them, they look a bit like the Odonata (dragonflies and damselflies) but they are only pale copies: Odonata are daunting hunters feared by all the insects! However, have you ever wondered if their reputation for living only one day -what gave them their name- is true? Actually, t’s actually not true.

First of all, mayflies do not form a whole species; it is an order (Ephemeroptera order) like Odonata or Lepidotera (butterflies and moths) for example, which includes a few thousand species.
Then let’s look a little closer at their life cycle! Mayflies come from eggs laid by previous generation females in aquatic environments. After a while, varying from several days to several months depending on ambient conditions notably the temperature, from each egg will emerge an aquatic larva called nymph or naiad. They are morphologically different from adults, including a lack of wings and a biology adapted to aquatic life. The nymphs will then grow up by successive molts in several months or even several years, depending on the specific species and ambient conditions. Finally they will reach subimago stage. This is a particular stage, where individuals are morphologically similar to adults (imago) with wing presence and biology adapted to the terrestrial world, but generally with unfinalized sexual organs and dull and bland colors. Often, this passage from nymph to subimago, from water to air, takes place simultaneously for all nymphs, so there can be swarms of thousands of ephemeral flying everywhere! And for anyone who likes to have insect on the menu, like birds, bats, or fish for example, it’s a manna, Christmas before time! Subimagos can molt once again to become imagos. These are the only insects to my knowledge that can molt once again after having functional wings. The life span of subimago+imago is short, from a few minutes to a few days depending on the species. Adults will search to breed and females will lay eggs in aquatic environments, and the cycle begins again!

In photo this is a mayfly of the Heptageniidae family. It’s a subimago male, and it’s hard to go further. I thought of a Heptagenia and I was confirmed that it was possibly this genus, even Heptagenia sulfurea, but another close genus (genus Dacnogenia) makes it impossible to be assertive.


Last update: January 4, 2021

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