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By Brandon & Walid. Stoneflies. Description: . 5-50mm in body length 2 long antennae eyes are widely separated gills are usually found on the throat and the base of the legs and abdomen 3 pairs of crablike legs with terminal tarsi with 2 tarsal claws 2 separate pairs of wing pads

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5-50mm in body length

2 long antennae

eyes are widely separated

gills are usually found on the throat and the base of the legs and abdomen

3 pairs of crablike legs with terminal tarsi with 2 tarsal claws

2 separate pairs of wing pads

2 long tails (cerci)

with over 460 species known to inhabit North American, colour is varied, however shades of yellow, orange, green, brown and black are the most common. Quite often stoneflies are 2 toned.

Adults:adult stoneflies look much the same as the nymphs with the following differences:

wings are folded flat over the back and often extend 10 to 20% past the tip of the abdomen

2 short tails (cerci)


What they look like:

Stonefly nymphs are often confused with Mayfly nymphs. Stonefly nymphs have two long tails or cerci (sir-key), whereas Mayfly nymphs have three long tails. The cerci are sense organs but also help the insect to move. Stonefly nymphs have tubes of thread-like gills on their underside, wing pads and antennae (feelers). Each leg has two claws that are used to cling to rocks or sticks. Their bodies are streamlined so they don't get swept away by the water current.


Habitat :

Stonefly nymphs require well oxygenated water so are consequently found in rivers and streams amongst the rocks and bottom debris, a few species can also be found in the rocky shoals of cold lakes.


Food chain

Stonefly nymphs eat dead plats and algae, they also feed on organic and vegetable matter found in the stream substrate, many species feast on leaves falling from streamside trees . Some species stalk their prey and are carnivorous eating other animals, feeding on mayfly nymphs and other insect larva. Many of stonefly adults do not eat, but those that live as adults longer do eat vegetation, pollen or nectar.


What’s interesting about the Stonefly Nymph?

Some take up to three years to develop into adults.

Adult Stoneflies live only for a week to a month, and females live longer than males.


Life Cycle of the Stonefly

Most female stoneflies skim the surface of the stream, dipping their abdomens in the water and releasing their eggs. Others will actually crawl to the bottom of the stream and then release their eggs on submerged objects. Stoneflies are very clumsy fliers and during the egg releasing procedure will cause quite a fluttering and splashing on the water surface which immediately attracts the attention of hungry fish especially steelhead. Highly ornamented eggs may hatch quickly or undergo long diapause. The nymphs grow through many instars (12 - 23). The length of the life cycle is 1 to 4 years. Mature nymphs move to shore and climb out of the water (mostly at night) before the final molt. Adults live for a few days to few weeks among shoreline vegetation or rocks and they feed little, if at all. Males attract mates by drumming, and mate while alighted. Females lay the eggs on or above the water. The eggs separate and sink to the bottom.



Well known with many faunal treatments and revisions available. Currently a popular group receiving much attention, which is resulting in many new discoveries and taxonomic changes. Many current names represent elevations in former ranks. Males, females, eggs, and nymphs are frequently identifiable to species.


Two pairs if present.

Both pairs membranous and clear.

Most species have moderate number of wing cross-veins that form long rectangular cells.

Few species have numerous cross-veins and cells.

Hindwings are shorter and wider than the forewings.

At rest, wings overlap and are held flat over body or often curving around the abdomen.

Generally cover the abdomen though a few species have short wings.


Harmful and benaficial

Harmful: AStonefly nymphs bite totally drains the blood of an adult human

Beneficial: most stonefly adults have not developed mouthparts and cannot bite.


Plecoptera, or stoneflies, is a small order of hemimetabolous insects: according to our data, more than 3,497 species have been described so far in the world. The total number of species has enormously increased in the last 30 years (2,000 species estimated in 1976) and, if the trend continues, then it will nearly double in the near future. The order is divided into the suborders Arctoperlaria and Antarctoperlaria, and includes 16 families: 12 arctoperlarian and 4 antarctoperlarian. The Arctoperlaria account for a total number of 3,179 species, and Antarctoperlaria, only 318 species. The total number of genera is 286. We give in this article the estimated number of species for each family. The fauna and diversity of stonefly in North America (650 species reported) and Europe (426 species) are best known. Nevertheless, in the last 25 years, a mean of 2.6 Plecoptera species per year were described in Europe. Stonefly-faunas of Australia (191 species, Tasmania included) and New Zealand (104 species) are relatively well-known, while our knowledge of the Plecoptera of Central and South America (95 and 378 species respectively) is poor and still not representative of the real diversity. Africa has a reduced stonefly fauna (126 species). Asian stonefly diversity (approximately 1,527 species) is much greater than that of Europe or North America despite the fact that, except for Japan and Asiatic Russia that have been well studied, our knowledge of the remaining Asiatic areas is extremely poor. Even though our data indicate the Holarctic Region as the diversity hot-spot for the order, the analysis of the specific diversity divided by family suggests also an important role of tropical stoneflies.


Basic anatomy

Stoneflies have a generalised anatomy, with few specialised features. they have simple mouth parts with chewing mandible, long multi segmented antennae, large compound eyes and have two or three ocelli. the legs are strong with each ending in two claws. the abdomen is relatively soft, and include remnants of the nymphal gills even in the adult. Both nymphs and adults have long paired cerci connecting from the tip of their abdomens.



Like many aquatic insects, stonefly naiads need clean water to live.  Because of this, scientists can tell if a stream is polluted or not based on whether stonefly naiads are present.  Read more about using insects to determine water quality.