Ephemeroptera - the mayflies

bug

penny
Note the size of the real penny and use it to judge the size of the bugs in the following pictures.

Family: Baetidae - Small Minnow Mayflies

adult Baetis
Baetis larva

Class: Insecta

Order: Ephemeroptera, the mayflies

Family: Baetidae, small minnow mayflies.

Size: 0.25 to 0.5 inch (3-12 mm)

Habitat & Habits: Baetid larvae live in streams, lakes and wetlands. Some species cling to aquatic plants while others prefer stream riffles. The streamlined larvae are good swimmers, moving in an undulating up and down motion. Larvae breathe through delicate gills on the back of their abdomen. Adults are small and delicate, living only a few hours to days to mate and lay eggs. Baetis adults and duns are commonly used as models for tied flies (bluewinged olive, etc.)

Feeding: Most Baetid larvae feed on detritus and algae.

Water Quality Indicator: Most baetid mayflies are moderately tolerant of nutrient enrichment.


Family: Ephemeridae - Common Burrowers

Adult Hexagenia

Class: Insecta

Order: Ephemeroptera, the mayflies

Family: Ephemeridae, common burrowers

Size: Larvae are 0.5 - 1.5 inches (12-35 mm) long; Hexagenia are our largest mayflies.

Habitat & Habits: Larvae dig U-shaped burrows in soft sediments of well-oxygenated rivers and lakes. Ephemera are more common in rivers, while Hexagenia are more common in lakes. Burrow openings are about the diameter of a pencil and may cover large areas of muddy bottom. Larvae may take up to 2 years to mature; adults emerge synchronously, often in large numbers, and live only a day. Fisherfolk fish these emergences (called "hatches"), and tie flies imitating the adults and larvae.

Feeding: Within the burrow, larvae undulate to form water currents bringing in oxygen and detritus for food. Adults do not feed.

Water Quality Indicator: Hexagenia are moderately tolerant of nutrient pollution, but are sensitive to low dissolved oxygen levels. Ephemera are very intolerant of pollution.


Family: Ephemerellidae - Spiny Crawler Mayflies

Larva - Coming soon!

adult Ephemerellidae

Class: Insecta

Order: Ephemeroptera, the mayflies

Family: Ephemerellidae, spiny crawler mayflies

Size: Larvae: 0.2-0.6 inches (5-15 mm).

Habitat & Habits: Larvae are common in streams and have hardened (operculate) gills along the back of their abdomen. Larvae are poor swimmers and cling to rocks, moss, or algae. Adults are terrestrial and short-lived. Fly fisherfolk often fish their emergences ("hatches").

Feeding: Larvae crawl about collecting detritus for food.

Water Quality Indicator: Most larvae are intolerant to moderately intolerant of nutrient pollution, and are fairly good water quality indicators.


Family: Heptageniidae - Flathead Mayflies

Rhithrogena larva
Adult Epeorus

Class: Insecta

Order: Ephemeroptera, the mayflies

Family: Heptageniidae, flathead mayflies

Size: Larvae: 0.2-0.8 inches (5-20 mm).

Habitat & Habits: Many larvae are extremely flattened, as if they had been steamrolled. Most larvae live in streams, but a few live in lakes. Some are adapted to live in very fast current. Larvae cling on and under rocks, and are poor swimmers. Adults are terrestrial and may live a week or more (an old age for mayflies). Fly fisherfolk often fish their emergences ("hatches").

Feeding: Larvae scrape algae and detritus off rocks for food.

Water Quality Indicator: Most larvae are intolerant to moderately intolerant of nutrient pollution, and are fairly good water quality indicators.