Order Plecoptera
Stoneflies
General Description
The name Plecoptera is derived from the Greek "pleco" meaning folded and "ptera" meaning wing, which refers to the pleated hind wings which fold under the front wings when the insect is at rest.
The Plecoptera are an ancient an beautiful order of insects with the earliest known fossils dating from the Permian, they are popularly known as Stoneflies (because they are often seen resting on stones). They are soft bodied small to medium sized hemimetabolous insects.
Morphological Characteristics
Immatures:
 | Antennae long, filiform |
| Body flattened, legs widely separated |
| Tracheal gills present as "tufts" behind the head, at base of legs, or around the anus |
| Each segment of thorax is covered by a large dorsal sclerite |
| Cerci long, multi-segmented |
Adults:
| Antennae long, filiform |
| Front wings long and narrow; M-Cu crossveins form distinctive boxes near center of front wing |
| Hind wings with anal area enlarges and forming a lobe, which is folded fanwise at rest, in which originate the name "Pleco-ptera". |
| Abdomen with 2 fairly long threadlike tails. |
| Mouth parts mandibulate. |
Biology
| Eggs are attached to vegetation or stones in the water. |
| Nymphs are aquatic, having 2 featherlike gills. |
| Undergo a simple metamorphosis. |
| Many species are active as adults in late fall, winter and early spring. |
| Nymphs live mostly in rivers or streams. Many species live also on lakes and ponds, acting as effective biological indicators of favourable environments Adults are found flying around these habitats or resting on rocks and vegetation nearby. |
| Most species at nymphal stage feed on detritus. They are not active fliers and usually remain near the ground where they feed. Some are plant feeders. Others are predatory on other aquatic insects. Adults feed on blue-green algae and vegetation. Others are predators and many do not eat at all. |
Distribution
Stoneflies are common in and around fast-moving streams in temperate and boreal climates. In North American there are some 465 species in 10 families; worldwide, there are over 2,000 species in 15 families.
Economic Importance
In order to survive, stoneflies require clean, well-oxygenated water, and thus they can be biological indicators. They are extremely sensitive to water pollution and are used by ecologists as indicators of water purity. Stoneflies are also an important source of food for game fish such as trout and bass.
Interesting Facts
| Stonefly eggs are coated with a sticky slime that adheres to rocks and keeps the eggs from washing away in fast moving water. |
| One species in the family Capniidae passes its entire life cycle in the depths of Lake Tahoe, U.S.A. |
Plecoptera
from MontanaPlecoptera Holdings at Cornell
Stoneflies (Plecoptera) Found in the Streams of the Kuril Islands and Adjacent Regions