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Order
- PLECOPTERA
(Greek, plekein = to fold; pteron = wing)
Common Name: stoneflies
Distribution: Cosmopolitan
Description
Stoneflies are soft bodied insects that generally have two unequal pairs
of membranous, intricately veined wings. However, there are some wingless
species. The forewings are smaller than the hind wings and are often
longer than the abdomen of the insect. Adult insects have large compound
eyes with two or three simple eyes (ocelli). The antennae are long and
composed of short, straight segments (filiform). The adult stage has
mandibles but these are often reduced. In some species they may be
functionless as the adult insect has not been observed to feed. Generally,
there are two appendages at the end of the abdomen (cerci).
Naiad
The juveniles emerge from the eggs as miniature replicas of the adults
(nymphs) but without wings. Nymphs mature through a series of moults, sometimes
as many as 33. The nymphs are aquatic and possess gills as a fringe along the
abdomen. The nymphs crawl about over the beds of fast flowing streams, although
they can swim if necessary. Stoneflies are very quickly affected by pollution as
they are unable to tolerate even minor levels of contaminants.
Members
Stoneflies.
Food
The nymphs may feed on plants, animals and detritus, or be restricted solely
to plants. Some nymphs are predators on small aquatic life. Adults feed on
algae, lichens, plants or even rotten wood.
Importance
No known importance apart from their presence in the food-chains of
freshwater communities. The stoneflies may be useful components in fish
food-chains.
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