Insect external structure
Insect internal structure
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Insect identification > Plecoptera
The most usual common name for the Plecoptera is stone flies. They range from small to good-sized insects whose bodies are quite long, flattened and with rather parallel sides. The wings are nearly always well developed and with many cross veins, though in a few cases they are very small and in some species the cross veins are few. In considering only the more usual condition, the forewings extend well behind the end of the body when closed and have a considerably smaller area than the hind wings which are so broad that when they are at rest upon the upper side of the body they must be folded lengthwise into plaits to reduce them to the necessary width.
The antennae are long and composed of many segments. In most members of the group a pair of cerci is present at the end of the abdomen. The mouth-parts are of the chewing type but are generally so weakly developed as to be practically useless. The nymphs live in water and do not differ greatly in appearance from the adults.
The group may be described as follows:
Insects which as adults have four membranous wings, usually longer than the body, and generally with many cross veins. Hind wings larger than the front ones and when at rest folded lengthwise and lying, covered by the front pair, on the abdomen. Antennae long; a pair of caudal cerci usually present; mouth-parts for chewing but generally poorly developed. Metamorphosis incomplete.