Mayfly larva or Cloeon dipterum

In our geographical area, especially in spring, nature is busy creating new life, such as these Mayfly larvas which will become adult insects in a few months.

Fig 1. - Mayfly adult. Mayfly, Leaf, Dew Image. Pixabay.com

Mayflies are aquatic insects belonging to the order Ephemeroptera. This order is part of an ancient group of insects termed the Palaeoptera, which also contains dragonflies and damselflies. Over 3,000 species of mayfly are known worldwide, grouped into over 400 genera in 42 families. 

In these images, you are seeing Mayfly larvae, which have a slender and soft-body like the adult insects. They do not have wings but have a series of leaf-like or feathery external gills attached along the sides or to the upper rear part of the abdomen. In the video, you can see them fluttering up and down. Their eyes are smaller than those of the adult insects.

Fig 2. - Mayfly larva or Cloeon dipterum. Motic SMZ-171

Moticam 1080. Image credit: Willem Cramer

As mentioned, adult mayflies are slender, soft-bodied, with four membranous, extensively veined wings held upright and together (like a butterfly). The forewings are much longer and often overlap the hindwings.

Mayflies play an important role in aquatic ecosystems, eating algae and other small objects and being eaten by larger animals. As winged adults, mayflies only live for a few days. The only function of the adult is reproduction. Their swarms often cause a feeding frenzy among fish.

Mayflies are the only insect to have two "mature" molts. They begin life as eggs that are laid on the surface of the water and sink to the bottom. The larvae of mayflies crawl around rocks and vegetation. After months or years of growth (depending on the species), they float to the surface and molt into a winged but sexually immature subadult. Often another molt occurs within hours and the final stage emerges - the reproductive adults who live for only days or hours.

Fig 3. - Mayfly larva or Cloeon dipterum. Motic SMZ-171

Moticam 1080. Image credit: Willem Cramer

In places where mayflies synchronize their maturation and mating cycles, appearing in swarms, they also usually cause fish to gather, and anglers create fly baits to resemble adult mayflies.

All life stages of mayflies are favorite foods for fish such as trout, perch and many others, as well as smaller aquatic predators in the food chain. Adult mayflies are also eaten by terrestrial predators such as spiders and birds.

Sample: Mayfly larva or Cloeon dipterum. Motic SMZ-171 Recorded with Moticam S12.