Plecoptera is an
order
Order, ORDER or Orders may refer to:
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
* Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...
of
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs ...
s, commonly known as stoneflies. Some 3,500 species are described worldwide, with new species still being discovered. Stoneflies are found worldwide, except Antarctica. Stoneflies are believed to be one of the most primitive groups of
Neoptera, with close relatives identified from the
Carboniferous and Lower
Permian
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Pale ...
geological periods, while true stoneflies are known from fossils only a bit younger. Their modern diversity, however, apparently is of
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Creta ...
origin.
Plecoptera are found in both the
Southern and
Northern Hemispheres, and the populations are quite distinct, although the
evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
ary evidence suggests species may have crossed the
equator
The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can al ...
on a number of occasions before once again becoming geographically isolated.
All species of Plecoptera are intolerant of
water pollution
Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Wate ...
, and their presence in a stream or still water is usually an indicator of good or excellent water quality.
Description and ecology

Stoneflies have a generalized anatomy, with few specialized features compared to other insects. They have simple
mouthparts
Mouthparts may refer to:
* The parts of a mouth
** Arthropod mouthparts
*** Insect mouthparts
{{disambig ...
with chewing
mandibles, long, multiple-segmented
antennae, large
compound eye
A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which dis ...
s, and two or three
ocelli
A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-le ...
. The legs are robust, with each ending in two claws. The
abdomen
The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the tors ...
is relatively soft, and may include remnants of the nymphal gills even in the adult. Both
nymph
A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are ty ...
s and adults have long, paired
cerci projecting from the tip of their abdomens.
The name "Plecoptera" literally means "
braid
A braid (also referred to as a plait) is a complex structure or pattern formed by interlacing two or more strands of flexible material such as textile yarns, wire, or hair.
The simplest and most common version is a flat, solid, three-strande ...
ed-wings", from the
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...
''plekein'' (πλέκειν, "to braid") and ''pteryx'' (πτέρυξ, "wing"). This refers to the complex venation of their two pairs of
wings
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is exp ...
, which are
membranous
A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. ...
and fold flat over their backs. Stoneflies are generally not strong fliers, and some species are entirely wingless.
A few wingless species, such as the
Lake Tahoe benthic stonefly
A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...
(''
"Capnia" lacustra'') or ''
Baikaloperla'', are the only known insects, perhaps with the exception of ''
Halobates'', that are exclusively aquatic from birth to death. Some
true water bugs (Nepomorpha) may also be fully aquatic for their entire lives, but can leave the water to travel.
The nymphs (technically, "naiads") are aquatic and live in the
benthic zone of well-oxygenated lakes and streams. A few species found in New Zealand and nearby islands have terrestrial nymphs, but even these inhabit only very moist environments. The nymphs physically resemble wingless adults, but often have external gills, which may be present on almost any part of the body. Nymphs can acquire oxygen via diffusing through the exoskeleton, or through gills located on behind the head, on the thorax, or around the anus. Due to their nymph's requirement for well oxygenated water, the species is very sensitive to water pollution. This makes them important indicators for water quality. Most species are herbivorous as nymphs, feeding on submerged leaves and benthic algae, but many are hunters of other aquatic arthropods.
Life cycle
The female can lay up to one thousand eggs. It will fly over the water and drop the eggs in the water. It also may hang on a rock or branch. Eggs are covered in a sticky coating which allows them to adhere to rocks without being swept away by swift currents.
The eggs typically take two to three weeks to hatch, but some species undergo
diapause, with the eggs remaining dormant throughout a dry season, and hatching only when conditions are suitable.
The insects remain in the nymphal form for one to four years, depending on species, and undergo from 12 to 36
molts before emerging and becoming terrestrial as adults. Before becoming adults, nymphs will leave the water, attach to a fixed surface and molt one last time.
The adults generally only survive for a few weeks, and emerge only during specific times of the year when resources are optimal. Some do not feed at all, but those that do are herbivorous.
Adults are not strong fliers and generally stay near the stream or lake they hatched from.
Systematics
Traditionally, the stoneflies were divided into two
suborder
Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...
s, the "Antarctoperlaria" (or "Archiperlaria") and the
Arctoperlaria. However, the former simply consists of the two most
basal
Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''.
Science
* Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure
* Basal (medicine), a minimal level that is nec ...
superfamilies of stoneflies, which do not seem to be each other's closest relatives. Thus, the "Antarctoperlaria" are not considered a natural group (despite some claims to the contrary).
The Arctoperlaria, though, have been divided into two
infraorder
Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...
s, the
Euholognatha (or
Filipalpia) and the
Systellognatha (also called
Setipalpia or
Subulipalpia). This corresponds to the
phylogeny
A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spe ...
with one exception: the
Scopuridae must be considered a basal family in the Arctoperlaria, not assignable to any of the infraorders. Alternatively, the Scopuridae were placed in an unranked
clade "Holognatha" together with the Euholognatha (meaning roughly "advanced Holognatha"), but the Scopuridae do not appear significantly closer to the Euholognatha than to the Systellognatha.
In addition, not adopting the clades Antarctoperlaria and Holognatha allows for a systematic layout of the Plecoptera that adequately reproduces phylogeny, while retaining the traditional
ranked taxa.
[Nelson (1996b)]

Basal lineages ("Antarctoperlaria")
* Superfamily
Eusthenioidea
** Family
Diamphipnoidae
Diamphipnoidae is a family of stoneflies in the order Plecoptera
Plecoptera is an order of insects, commonly known as stoneflies. Some 3,500 species are described worldwide, with new species still being discovered. Stoneflies are found world ...
** Family
Eustheniidae
* Superfamily
Leptoperloidea
** Family
Austroperlidae
Austroperlidae is a family of stonefly, stoneflies in the order Plecoptera. There are about 10 genera and 15 described species in Austroperlidae across southern land masses Australia, New Zealand, and South America.Austroperlidae species are uniq ...
** Family
Gripopterygidae
Gripopterygidae is a family of stoneflies in the order Plecoptera. There are more than 50 genera and 320 described species in Gripopterygidae.
Genera
These 57 genera belong to the family Gripopterygidae:
* '' Acroperla'' McLellan, 1977
* '' A ...
Suborder
Arctoperlaria
* Basal family
Scopuridae
* Infraorder
Euholognatha
** Family
Capniidae
The Capniidae, the small winter stoneflies, are a family of insects in the stonefly order (Plecoptera). It constitutes one of the largest stonefly families, containing some 300 species distributed throughout the holarctic. Their closest relative ...
(about 300 species) – small winter stoneflies
** Family
Leuctridae
The Leuctridae are a family of stoneflies. They are known commonly as rolled-winged stoneflies (390+ species) – rolled-winged stoneflies
** Family
Nemouridae
The Nemouridae are a family of stoneflies containing more than 700 described species, occurring primarily in the Holarctic region.Nelson, C. Riley. 1996. Nemouridae. Version 1 January 1996 (under construction). http://tolweb.org/Nemouridae/1394 ...
(over 700 species) – spring stoneflies
** Family
Notonemouridae
Notonemouridae is a family of stoneflies in the order Plecoptera. There are more than 20 genera and at least 120 described species in Notonemouridae.
Genera
These 23 genera belong to the family Notonemouridae:
* '' Afronemoura'' Illies, 1981
* ...
** Family
Taeniopterygidae
Taeniopterygidae are a family of stone flies with about 110 described extant species. They are commonly called willowflies or winter stoneflies and have a holarctic distribution. Adults are usually smaller than 15 mm.
Genera
These 21 gener ...
(about 110 species) – winter stoneflies
* Infraorder
Systellognatha
** Family
Chloroperlidae
Chloroperlidae are a family of stoneflies, commonly known as green stoneflies, with more than 200 species and 22 genera. They appear green to yellow in colour, and are popularly used among fisherman as bait for trout fishing. Green stoneflies l ...
(over 180 species) – green stoneflies
** Family
Perlidae (about 400 species) – common stoneflies
** Family
Perlodidae (350+ species)
** Family
Peltoperlidae (about 68 species) – roachlike stoneflies
** Family
Styloperlidae
Styloperlidae is a family of stoneflies in the order Plecoptera. There are at least 2 genera and 9 described species in Styloperlidae. The species etymology is based on the type locality near Sapa.
History
The Styloperlidae family was original ...
(about 10 species)
** Family
Pteronarcyidae (about 12 species) – salmonflies, giant stoneflies
Notes
References
External links
*
*
* Plecoptera Species File
order Plecoptera (Version 5.0/5.0)
{{DEFAULTSORT:Plecoptera
Insect orders
Extant Permian first appearances
Taxa named by Hermann Burmeister
Symbols of Delaware
Aquatic insects
Polyneoptera