Common Two-Wing (Cloeon dipterum) - closeup, Heesch, Netherlands

Here we are at the 2nd night of my moth light trap, another by-catch. A personal highlight as I've never seen a mayfly in my life before this day. I believe this to be the female imago of the Cloeon dipterum. Two interesting facts about this species:

- The only species in Europe that is ovoviviparous, which means embryos are fully developed within the eggs still in the female. They hatch immediately after being deposited in the water.
- An interesting case of sexual dimorphism, where the male has an extra set of superposition tube-like eyes that allegedly help in spotting females in the midst of a crowded swarm. Here's a closeup of the superposition eyes:

https://commons.wikimedia.org/wiki/Cloeon_dipterum#/media/File:Cloeon_dipterum_Turbanaugen.jpg

On a live specimen by @Arp:

Keys used to come to this ID:
- orange-brown ridge on wings
- position: standing
- Numbers of tails: 2
- Tail type: ringed
- Abdomen: pattern on all segments

This leads to a single match in this excellent mayfly identification tool:
https://determineren.nederlandsesoorten.nl/linnaeus_ng/app/views/matrixkey/index.php?epi=107