Plecoptera Introduction

Adult stoneflies are soft-bodied, 2-5 cm long, with a brown and gray body. They usually have two pairs of wings; they fly readily, but not well. Antennae are long, and the cerci are well developed. Mouthparts are the chewing type, but they are weak. Nymphs resemble the adults, exceptfor the lack of wings; they have external filamentous gills on the thorax and legs. Most species live in cool, running streams, or in cold mountain lakes. Plecopterans are an important component in aquatic food chains, especially for fish. Adult stoneflies are imitated in the design of fishing fly used by anglers. These insects are physiologically fragile and intolerant of water conditions of low oxygen or pollution, and they are useful indicators of these and other stream conditions. Pest status of stoneflies is linked to their appearance in large numbers in areas adjacent to breeding sites, and sometimes a long distance from water. These incidents are usually associated with one or two species. Adults of Perla and Pteronarcys are attracted to lights at night.

Mating in stoneflies involves males attracting females by rubbing, tapping, or drumming a species-specific signal on an available substrate. Females respond to the male's vibrational signals with acoustic signals of their own. Male stonefly mating calls vary from a series of single beats to complex patterns of beats and intervals. These sounds are produced by a hammerlike structure on the underside of the abdomen. This morphological feature of the adult is struck or rubbed against the ground or other substrate. A few species in the Chlorperlidae produce sound by rapid vibration of their body, which is transferred to the substrate through the legs and tarsi. For most species, the males and females call back and forth, with some overlap (duetting) of the sounds. Males typically engage in a sequence of drumming and searching until a receptive female is located. Mating occurs immediately when male and female meet, and oviposition usually occurs soon after.

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