Mayfly nymphs, (Ephemeroptera)
Lifespan of adult mayflies ranged from several hours to two days. Depends on the species and ambient temperature plays a role too. The adult lifespan is so short there is no need for the insect to feed and therefore the adult does not possess functional mouthparts and digestive tract. Consequently, the majority of their life is lived out in the nymph stage and serve as important food source for fish. The way of life of the nymphs is highly diverse. They eat mostly plant food, especially algae and detritus – small particles of organic matter in various stages of decomposition. Most of the nymphs of mayflies have three caudal filaments, gills on the sides of the abdomen and each leg equipped with the single tarsal claw. Nymphs are adapted to specific aquatic environment and thus we can distinguish several basic types according to body shape.
Order: Ephemeroptera (Mayflies), Family: Heptageniidae (Flathead Mayflies, clingers)
Nymphs with a substantially flattened body, legs spread to the sides and eyes on the back of the head are perfectly adapted to live under the rocks. (This is known behavior of fish turning stones to find the nymphs.) Due to the shape of the body and strong legs ending in claws are able to maintain and move in fast flowing waters, when searching for food. Heptageniid nymphs are clinging scrapers that feed on algae attached to the surface of stones, wood and aquatic plants.
Order: Ephemeroptera (Mayflies), Family: Baetidae (Minnow Mayflies, swimmers)
Nymphs of tightening streamlined body shape are very skilled swimmers, hence the name Minnow mayflies. They have a rounded head bearing a pair of long antennae, rapidly oscillating plate-like gills on the sides of the abdomen and three long hairy filaments. By synchronizing the movements of these body parts can quickly escape the predators. They feed on plant matter and organic debris.
Order: Ephemeroptera (Mayflies), Family: Ephemeridae (Common burrowing Mayflies)
Burrowing nymphs with a long cylindrical body are found in the soft silt or sand at the bottom. Upturned mandibular tusks near the mouthparts and strong front legs help when burrowing. Ephemerid nymphs create a current of water through the U-shaped burrows by moving their branched gills. This current brings oxygenated water and detritus which they feed on.