How long does a mayfly live?

Despite their name, mayflies are active during the warmer months of the year, not just May. They tend to be gray, yellow, or brown and have long, thin abdomens. Mayfly larvae are aquatic and found in nearly all types of water bodies, from streams to lakes. The larva is often used as a bioindicator species to measure the health of water. Mayflies can vary in size, growing anywhere from a quarter-inch (0.6 centimeters) to 1.1 inches (2.8 centimeters).

Females deposit eggs in the water. Mayflies spend most of their lives in the water as nymphs and then emerge as adults for only a short while. Adults will live only a day or so, but the aquatic larvae lives for about a year.