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Mayflies: Order Ephemeroptera

Identification: Small to medium-sized, elongate, very soft-bodied, usually found near water. FW large, triangular, many-veined. HW small and rounded (rarely absent). Wings held together above body at rest. Abdomen with 2 or 3 hairlike tails. Antennae small, bristlelike, inconspicuous. Tarsi 3- to 5-segmented. Mouth parts vestigial. Metamorphosis simple.

Similar orders: (1) Odonata (p. 68): HW as large as FW or larger; terminal abdominal appendages relatively short; harder-bodied. (2) Hymenoptera (some ichneumons), p. 312: harder-bodied; antennae long; wings with fewer veins; tarsi 5-segmented. (3) Plecoptera (p. 92): HW with an anal lobe; wings held flat over abdomen at rest; antennae long and conspicuous. Immature stages: Leaflike gills along sides of abdomen, and 3

hairlike tails. Common inhabitants of ponds and streams. Food consists of small aquatic organisms and organic debris. Habits: The last nymphal instar molts to the winged form at the water surface or on an object just out of water. This winged stage, usually rathe- dull in appearance and somewhat pubescent, is not yet adult and is called a subimago; it molts once more to become adult (mayflies are unique among insects in undergoing a molt after the wings become functional). Adults seldom live more than a day or two, and do not feed. Males of many species engage in swarming flights, the members of the swarm flying up and down in unison. Eggs are attached to stones and other objects in the water, or are washed off the abdomen onto the water's surface. Adults often emerge in large numbers from lakes and ponds, and sometimes actually pile up along the shore.

Importance: Adults and nymphs are an important food of many freshwater fish. Artificial flies used by fishermen are often modeled after mayflies.

Classification: Three families, separated chiefly by wing venation and tarsal segmentation.

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