Mayflies are fascinating insects belonging to the order Ephemeroptera (from the Greek ephemeros, meaning "short-lived," and ptera, meaning "wings"). They are known for their incredibly brief adult lifespan, often living just a few hours to a couple of days. Here are some key characteristics and facts about mayflies:

1. Life Cycle:

Eggs: Laid in freshwater by females, often in large numbers.
Nymphs (Larval Stage): Live underwater for months to years (depending on species), feeding on algae and detritus. They are important aquatic indicators of water quality.
Subimago: A unique winged but sexually immature stage (not present in most other insects). They molt one final time to become adults.
Adult (Imago): Short-lived, focused solely on reproduction. Adults do not eat; their mouthparts are non-functional.

2. Physical Features:

Wings: Two pairs (forewings larger, hindwings smaller or absent), held upright like a sail.
Tail Filaments: Two or three long, thread-like appendages at the abdomen's tip.
Eyes: Males often have large, turban-like eyes to help locate females in swarms.

3. Ecological Importance:

Food Source: Nymphs and adults are crucial prey for fish, birds, and other aquatic predators.
Water Quality Indicators: Sensitive to pollution, their presence often signals clean water.
Nutrient Cycling: Their mass emergences contribute nutrients to ecosystems.

4. Behavior & Swarming:

Mass Emergence: Many species synchronize their emergence, creating dramatic swarms near water bodies.
Mating Flight: Males form dancing swarms to attract females, which fly in to mate mid-air.
Short Adult Life: After mating, females lay eggs and die, often within 24–48 hours.

5. Cultural & Fishing Significance:

Fly Fishing: Mayfly nymphs and adults are imitated by artificial flies (e.g., "Adams," "Blue-Winged Olive").
Symbolism: Their fleeting life has inspired poetry and art as a metaphor for transience.

6. Interesting Facts:

One of the oldest winged insect groups (~300 million years old).
Some species have a subimago stage, a rare trait where they molt after gaining wings.
The "ephemeral" nature of their adult life is legendary—some species live less than an hour as adults.

Would you like details on a specific aspect of mayflies, such as their role in ecosystems or their life cycle in more depth?