FAMILIES OF PLECOPTERA OF BRITISH COLUMBIA
R. A. Cannings and G. G. E. Scudder
Copyright © 2005 - All rights reserved
Key to Families of Plecoptera
1. Labium with glossae and paraglossae about same size and length, and set at the same level .................................................................................................
- Labium with glossae much smaller than paraglossae and set below the paraglossae ...................................................................................................................7
2. Forewing with two complete rows of several anal crossveins, these sometimes broken into an irregular network; abdomen with remnants of tufted gills on segments 1-2 or 2-3 .............................................................
- Forewing without anal crossveins beyond the anal cell; abdomen without remnants of tufted gills............................................................................................. 3
3. Head with 2 ocelli; all 3 thoracic segments with remnants of double gills .................................................................................................Peltoperlidae
- Head with 3 ocelli; thoracic segments 2 and 3 without gills.................................. 4
4. Tarsi with second tarsomere more or less equal in length to first tarsomere
- Tarsi with second tarsomere much shorter than the first tarsomere...................... 5
5. Cerci unsegmented; forewings with 2A forked, and with usually 5 or more intercubital crossveins .................................................................................6
- Cerci with many segments; forewings with 2A simple and unforked, and with usually 1-2 intercubital crossveins ....................................................Capniidae
6. When at rest, wings folded flat over dorsum; labial palp with terminal segment circular in outline when viewed from below, and much larger than preceding segment .....................................................................................Nemouridae
- When at rest, wings folded in such a manner that they cover both the dorsum and sides of the abdomen; labial palp with terminal segment not circular in outline when viewed from below, but elongate and more or less the same size as the preceding segment .......................................................................Leuctridae
7. Forewings with cubito-anal crossvein reaching anal cell, or not distant from it by more than its own length; abdomen with remnants of branched gills laterally .........................................................................................................Perlidae
- Forewings with cubito-anal crossvein removed from anal cell by at least its own length; usually without gill remnants laterally, but at most with remnants of simple unbranched gills on thorax only......................................................... 8
8. Forewing with branching of 2A included in anal cell, the two branches leaving the cell at two separate points or (less often) at the same point.......................... 9
- Forewing with branching of 2A occurring beyond anal cell, or 2A unbranched
............................................................Chloroperlidae (except Kathroperla)
9. Head with portion behind the eyes as long as or longer than portion in front of eyes............................................................... Kathroperla (Chloroperlidae)
- Head with portion of head behind eyes shorter than portion in front of eyes Perlodidae
Description of Families
In the labium, the paraglossae and glossae are the same length. Larvae are herbivores and generally are coloured in browns and greys.
The Capniidae are the Small Winter Stoneflies, denizens of flowing waters from large rivers to cold mountain creeks and wave-washed, rocky lakes in the temperate regions of the Northern Hemisphere. Larvae probably live much of the time deep in the gravel and rocks in the bottom of streams or lakes; their slender bodies and lack of delicate gills are adaptations to this habitat. Adults emerge during winter or early spring, often between the water surface and the overlying ice, and frequently appear on the snow along the shoreline. There are about 250 described species, with ten genera and over 150 species in North America. There are six genera and 31 species in B.C. Capnia is the largest genus of the family in western North America, Allocapnia in the East.
The adults are small and slender, about 5 to 25 mm long (usually less than 10 mm), black or dark brown in colour. Three ocelli are present. There are no remnants of larval gills. The forewing does not have crossveins in the anal area; there are normally fewer than 10 costal crossveins and only one or two crossveins between Cu and M.. Many species have short-winged forms. The second tarsal segment is small and wedge shaped, much shorter than the first and third segments. Cerci are long, consisting of at least four segments.
The larvae are elongate and slender, the extended legs not reaching past the end of the abdomen. The wingpads are parallel to the body axis; the hindwing pads of normal-winged individuals are no more than twice as long as wide. Gills are absent and, as in adults, the second tarsal segment is wedge shaped and shorter than segment 1. There is a membranous fold on the sides of abdominal segments 1 to 9; abdominal terga are widest posteriorly and almost always have a posterior fringe of setae.
Bolshecapnia is restricted to the mountains of western North America, mostly from B.C. and Alberta to Montana. Four of the five species occur in B.C., and two of them -- B. gregsoni (Ricker) from southern B.C. and B. rogozera (Ricker) from the far northwest -- are not known outside the province. In southeastern B.C., B. spenceri (Ricker) lives in cold mountain streams and alpine lakes where gravel bottoms and cold waveswept shallows simulate flowing streams; adults do not emerge until late June through August. Most of the 52 North American species of Capnia are western; 14 live in B.C., making it the largest genus of B.C. stoneflies. C. nana Claassen is widespread in western mountains and is by far most common capniid of small mountain streams. C. cheama Ricker lives in large streams and rivers such as the Fraser; although it ranges widely, north almost to the Arctic Ocean, it is rare. C. nearctica Banks lives across the boreal forests and ranges to Baffin Island in the east and Far-eastern Russia in the west; in B.C. it is known only from Atlin.
Eucapnopsis brevicauda (Claassen), the sole North American species in the genus, occurs from Alaska and the Yukon south to New Mexico. It is common in B.C. Young larvae do not grow until fall, then emerge as adults from February to July, depending on latitude and altitude. The genus Isocapnia also lives in western North America and northeastern Asia; there are five species in B.C. Most species live in large creeks and rivers with rocky or gravelly bottoms. Mesocapnia is almost completely western in North America. M. variablilis (Klapalek) lives on both sides of the Bering Strait, from Siberia to the Yukon; it occurs at Summit Lake in northeastern B.C. The other three B.C. species range south to Oregon or California. All ten species of Utacapnia are North American, and nine of these are western, living mostly in the Rocky Mountains and adjacent ranges; there are two in B.C.
These are the Rolled-winged Stoneflies, so-called because the small, slender species roll the edges of their wings around the sides of their bodies. The larvae eat detritus and algae in streams, especially those associated with springs; adults usually emerge in spring and early summer. There are about 200 species in Northern Eurasia, eastern Asia and North America. Nine genera and 55 species are recognized in North America; B.C. has five genera containing nine species.
Adults are small (6 to 10 mm long) and dark. The forewing has 4 or more crossveins between Cu and M and fewer than 10 costal crossveins; the apical crossvein (a slanting vein joining C and R1 along the front of the wing near the tip) is absent. The first and third tarsal segments are much longer than the second segment. There are no gill remnants and the cerci have only one segment.
The larvae are elongate: the abdomen is often longer than the length of the head and thorax combined and the extended hindlegs reach far short of the end of the abdomen. The second tarsal segment is wedge-shaped and shorter than segment 1; the hindwing pads lie parallel to the body and are usually more than twice as long as wide. The membranous fold on the side of the abdomen is short, at most extending to segment 7; the abdominal tergites are parallel-sided and, unlike those of the Capniidae, often do not have a posterior fringe of setae.
Despaxia contains only one species, D. augusta (Banks), a common stonefly of creeks in the western mountains. It occurs all over B.C. and is an autumn species, emerging from August to November in the province. Megaleuctra species are typical of spring outlets; in general they are rare. M. stigmata (Banks), the only species known in B.C., has been found in the Purcell Mountains. There is only one species of Moselia -- M. infuscata (Claassen) is an inhabitant of the Coast and Cascade Mountains from southern B.C. to California. The larvae are especially setose. The four species of Paraleuctra known in B.C. range throughout the province; these are spring and summer emergers. All range from Alaska and the Yukon south: P. forcipata (Frison) to Montana and Oregon, P. purcellana (Neave) to Wyoming, P. occidentalis (Banks) and P. vershina Gaufin and Ricker to New Mexico. Both North American species of Perlomyia live in the western mountains and both occur in B.C.; they are usually associated with springs and spring-fed streams. P. collaris Banks and P. utahensis Needham and Claassen have been collected mainly on the south coast, but both no doubt occur throughout the province.
The Nemouridae is a large family of about 400 species in northern Eurasia, east Asia and North America. North America has 12 genera and 71 species; B.C. records nine of these genera and 17 species. Nemourids are often termed Spring Stoneflies because they typically emerge from April through June. Larvae are usually stout and brown and live among rocks in cool running (sometimes standing) water. They feed on algae, leaves and detritus.
Adults are 5 to 15 mm long and dark coloured. The forewing has four or more crossveins between Cu and M and there are fewer than 10 costal crossveins. An apical crossvein (a slanting vein joining C and R1 on the front edge of the wing near the tip) is present. The pattern of veins forms a characteristic x-shaped mark near the wing apex. Many species have a windowed, mottled or barred wing pattern. The first and third tarsal segments are much longer than the second. The cerci have one segment.
Larvae are relatively robust, the extended hindlegs reaching the end of the abdomen. The wingpads in mature larvae are strongly divergent (“swept-wing” form), unlike those of the Capniidae and Leuctridae. Gills are often present under the head and neck, but there are no coxal gills. The second tarsal segment is wedge-shaped and shorter than the first.
Amphinemura linda (Ricker) is the sole boreal member of its genus; it is widespread in northern B.C. Another northern B.C. stonefly is Nemoura arctica Ebsen-Petersen, a species that ranges from Europe and northern Asia to Alaska and Quebec. All Malenka species are from western North America; the two B.C. species are common in small creeks in southern B.C. M. californica (Claassen) emerges mostly in the fall, M. cornuta (Claassen) mostly in spring and early summer. Both of the western North American species of Ostrocerca live in B.C.; the other four are eastern. O. dimicki (Frison) and O. foersteri (Ricker) occur in streams at lower elevations on the south coast and range south into Oregon. Podmosta decepta (Frison) and P. delicatula (Claassen) range from the Yukon to Utah and Wyoming, respectively; both are widespread in B.C. Prostoia is strictly North American, and three of the four species are eastern. P. besametsa (Ricker) is common and widespread in B.C.; in the south adults appear in April and May from both large rivers and creeks. Soyedina interrupta (Claassen) is known from Canada only in the Fraser Valley; it probably is restricted to the Cascade region, ranging south to Oregon. S. producta (Claassen) is a little more widespread on the south coast, but has a similar geographical range.
Visoka cataractae (Neave), a stonefly of small cold streams in the western mountains, is the only species in its genus. It has been collected from Vancouver Island to the Rockies. Zapada is the largest genus of Nemouridae in B.C. with five species; all of these range from Alaska and the Yukon south along the mountains to varying degrees. Z. cinctipes (Banks) is the most common of a number of widespread Zapada species in the province; the larva has the distinctive circlets of spines around the femora that are characteristic of the genus.
The Taeniopterygidae is a Holarctic family with three genera found in both the Old and New worlds. Taeniopteryx and Oemopteryx are eastern north American and European while Taenionema is western North American and east Asian. Other genera are less widespread. There are about 100 species named in the world and six genera and 34 species in North America. B.C. has two genera and four species. Larvae live in a range of streams from large rivers to small creeks and feed on algae, leaves and detritus. Adults emerge in the winter and spring and tend to rest on twigs and bushes instead of rocks, as is the habit of many stoneflies. They are often called Winter Stoneflies.
Adults are medium-sized stoneflies, 8 to 15 mm long and brown or black. The antennae are long, but the cerci are short (one segment in males, up to six in females). The forewing has no crossveins in the anal area and there are fewer than 10 costal crossveins. The length of the second tarsal segment is about equal to the first.
Mature larvae have the same swept-back, divergent wingpads as the Nemouridae, but are distinguished from that family and the related Capniidae and Leuctridae in having the second tarsal segment as long as, or longer than, the first one. Of the North American genera, only Taeniopteryx has gills (finger-like coxal ones). In the B.C. genera, both male and female larvae have an enlarged, shield-like sternum 9.
Doddsia occidentalis (Banks), the single North American species in the genus, occurs all over B.C.; its complete range extends from Alaska to New Mexico and California. It prefers medium-sized streams and rivers. Eleven of the 12 North American species of Taenionema are western; the three B.C. species range from the Yukon south into the U.S.A. T. pacificum (Banks) is black with red and yellow markings and measures 13 mm to the tips of the wings. Adults appear in March and April and feed on alder, willow and rose foliage. They have also eaten the flower buds of apricots, peaches and plums, causing deformed fruit -- T. pacificum has the distinction of being the only stonefly accused of damaging crops.
In the labium, the paraglossae are significantly longer than the glossae; mandibles are reduced in adults. Larvae are primarily carnivorous and generally marked with contrasting light and dark colours.
As the scientific name suggests, the Chloroperlidae are the Green Stoneflies, small to medium-sized species (6 to 20 mm), many of which are pale yellow or green (members of the Subfamily Paraperlinae – Kathroperla, Parperla, Utaperla -- are brown or black, and sometimes as long as 40 mm). Larvae live in a wide variety of habitats from cold rocky-bottomed lakes to small spring trickles, rushing mountain creeks and large rivers. The larvae of many genera live within the gravel of the stream or lake bottom. When young, they are omnivorous, but become more generally carnivorous as they mature, eating chironomid midge, mayfly, caddisfly and stonefly larvae. Development normally takes a year, the adults usually emerging in the spring or summer. Adults do not feed, but fly actively, landing on plants for camouflage. Chloroperlids inhabit the temperate regions of Eurasia and North America; some genera, such as Alloperla, Suwallia, Sweltsa and Triznaka occur in both the Old and New worlds. About 125 species are described, with 12 genera and 89 species in North America. Nine genera containing 28 species are recorded in B.C.
Adults are often green or yellow, sometimes with a dark dorsal stripe. In the forewings there are several to many crossveins between Cu and M and the anal area of the hindwing is reduced (3 or fewer veins)or is absent. The pronotum is more or less oval. The third tarsal segment is much longer than the first one. Remnants of larval gills are never present and the cerci are distinctly longer than the width of the pronotum.
Larval mouthparts have the paraglossae much more developed than the glossae and the apical segment of the maxillary palp is small and set asymmetrically on the penultimate segment. The top of the thorax usually lacks a distinct pattern and the hindwing pads lie parallel to the body or are only weakly divergent. There are no coxal gills. The second tarsal segment is wedge-shaped and shorter than the first segment. The cerci are three-quarters or less the length of the abdomen.
Alloperla is a large genus with 29 described species in North America; only seven are western and 5 of these live in B.C. The adults are yellow to light green. The most common and widespread species in the province is A. severa (Hagen), which occurs from Alaska and the Yukon south to Colorado and California. Haploperla brevis (Banks) is a boreal and Appalachian species that in B.C. has been collected only in the northern interior; it is unknown from the western U.S.A. H. chilnualna (Ricker), however, ranges from southern Vancouver Island to Baja California in coastal streams. The two species of Kathroperla are strictly western North American; K. perdita Banks is a common B.C. species that emerges from April through June; the larvae evidently live within the gravel of streambeds. Plumiperla diversa (Frison) occurs throughout the western mountains of North America and on the Kamchatka Peninsula of eastern Russia.
Suwallia species are yellow and 6 to 10 mm long; they emerge in summer and early fall. The most common of the five species in B.C. is S. pallidula (Banks). The largest chloroperlid genus in B.C. is Sweltsa, named for the aboriginal name of the outlet of Cultus Lake, near Chilliwack, by William Ricker, well-known B.C. expert on Plecoptera. This genus occurs in both the Old and New worlds; there are 27 North American species, 20 of which are western. There are nine recorded in B.C.; some of these are very common, especially S. fidelis (Banks). Other genera found in B.C. are Paraperla (two species), Triznaka (two species) and Utaperla (one species)
These are the so-called Roach-like Stoneflies, which, with the short abdomen, broad thorax and hidden, hypognathous head of the larva, somewhat resemble cockroaches. The larvae live in cold streams and springs where they eat decaying leaves and detritus. Adults emerge in late spring and summer. The 35 world species are restricted to North America and eastern Asia; there are six genera and 20 species in North America. Three genera are Appalachian and three, including the only B.C. genus, Yoraperla, live in the western mountains.
Adults are brown, 9 to 20 mm long; there are only two ocelli. The anal area of the forewing has no crossveins and gill remnants are absent from the body. The cerci are short, no longer than the width of the pronotum. Larvae have the pronotum at least 1.5 times as wide as the head and, as in the adults, there are two ocelli. The thoracic sterna are shield-like, overlapping, and bear a posterior row of setae. Coxal gills are absent. The second tarsal segment is wedge-shaped and shorter than segment 1.
There are two species of Yoraperla in B.C. Yoraperla brevis (Banks) is widespread in the mountains of the south and ranges to California and Wyoming. It can be common in cold creeks and rivers, specially where there are accumulations of woody debris. Yoraperla mariana (Ricker), first discovered near Cultus Lake, has never been collected elsewhere in B.C.; it apparently is restricted to the Cascade Mountains and lives as far south as California.
The Perlidae is one of the largest stonefly families with 375 species worldwide. There are 15 genera and 75 species in North America. Although the family often goes by the name “Common Stoneflies”, with only five species in four genera in B.C., it is not diverse in the province. Several of the species are widespread and common in B.C., however. The predaceous larvae live in streams and may take up to three years to develop. Adults appear in spring and summer. They are small to large, ranging from 10 to 40 mm long, and are usually coloured in browns or yellows.. The third tarsal segment is much longer than the first segment. The forewing has several to many crossveins between Cu and M. Remnants of branched larval gills occur underneath the thorax at the bases of the legs. The cerci are distinctly longer than the width of the pronotum. Larvae have highly branched gills on the sides and underside of all thoracic segments and on abdominal segment 1.
Calineuria californica (Banks) is the only member of its genus in North America (its closest relatives are in eastern Asia) and ranges from B.C. and Alberta south to Montana and California. It is common and widespread in southern B.C. The striking brown and yellow larvae are predators of the larvae of chironomid midges, mayflies and caddisflies. Claassenia sabulosa (Banks) is a boreal species widespread in the B.C. interior. It has a two-to three-year life cycle. There are only two Doroneuria species; both occur in B.C. where D. theodora (Needham and Claassen) is more common than D. baumanni Stark and Gaufin. Hesperoperla pacifica (Banks) is probably the most abundant and widespread species of the Perlidae in B.C. It ranges from Alaska and the Yukon to California and New Mexico and east to Saskatchewan.. Larvae are voracious predators of insects in streams and rivers; adults are yellow-brown and large, up to 30 mm long.
The perlodids show great variation of size and colour, from small species only 5 to 10 mm long to large ones over 50 mm, from pale yellow and green species to brown and black ones. Adults normally do not feed and die soon after mating, although some are known to eat pollen. The carnivorous larvae are often coloured in contrasting dark and light patterns. They live in a variety of streams from cold, fast-flowing creeks to large rivers; they generally have one generation per year. The family is mostly Holarctic and about 200 species are described. There are 30 genera and 122 species known in North America; B.C. has 13 genera and 31 species. Although in B.C. there are an equal number of recorded species of Perlodidae and Capniidae, the former family has twice the number of genera.
The pronotum is usually rectangular, separating the perlodids from the related chloroperlids, which have a more oval pronotum. The forewing has several to many crossveins between Cu and M and the anal area of the hindwing is broad and fanlike. The third tarsal segment is much longer than the first one. There are no remnants of larval gills underneath the thorax, but finger-like remnants usually occur under the head. Males usually have a lobe on the hind margin of sternum 7; tergum 10 is deeply notched. The cerci are distinctly longer than the width of the pronotum.
The larvae have the top of the thorax typically patterned with contrasting colours; the hindwing pads in mature larvae diverge from the body axis. Coxal gills are normally absent, but if present, they are finger-like. The second tarsal segment is wedge-shaped and shorter than the first segment. In the labium, the paraglossa is much longer than the glossa; the apical segment of the maxillary palp is symmetrical with, and about equal in length to, the penultimate segment. The cerci are as long as, or longer than, the abdomen.
Arcynopteryx compacta MacLachlan is the only one of five species in the genus that lives in both the Old and New worlds, and the only one in North America, where it is a common boreal species. It is only recorded from Atlin in B.C., but probably is more widespread in the north in cold streams and along the stony shores of lakes. Cascadoperla has a single species, C. trictura (Hoppe), ranging in the mountains from the Fraser Valley of B.C. to California and Montana. The six species of Cultus are divided equally between eastern and western North America and all the western ones occur in B.C. Cultus aestivalis (Needham and Claassen) is common and widespread in the province; in a Colorado study, larvae fed almost exclusively on the larvae of chironomid midges and black flies.
Isoperla, with 58 North American species (and more in Eurasia) is by far the largest genus of the family. Eleven of these species are recorded in B.C. The adults usually have a green or yellow body and green wings; the larvae have no gills and often the abdomen has longitudinal dark and light stripes. I. decolorata (Walker) has a western boreal distribution and is known from only the far north of the province. I. fulva Claassen, I. petersoni Needham and Christenson and I. sobria (Hagen) are perhaps the most common species of the genus in B.C. Kogotus nonus (Needham and Claassen) and K. modestus (Banks) make up the genus Kogotus, a strictly western montane group; both species occur in the province.
Megarcys ranges from northeastern Asia to western North America; B.C., has four of the five American species. M. signata (Hagen) is certainly the most widespread and common, living in swift mountain streams all over the interior, north to the Yukon. Both the North American species of Skwala occur in the province – S. curvata (Hanson) lives from southern B.C. to Oregon and Wyoming and S. americana (Klapalek), the more common of the two, ranges from the Yukon to New Mexico. The larvae are voracious predators of aquatic insect larvae. Other genera of Perlodidae found in B.C. are Diura (one species), Frisonia (one species), Isogenoides (two species), Osobenus (one species) and Setvena (two species).
The small family Pteronarcyidae contains some of the largest stoneflies, and is often referred to as the Giant Stonefly family. Although once classed with the Euholognatha, the family’s herbivorous habits are considered to be secondarily developed. The larvae feed largely on leaves, algae and organic material. The adults are nocturnal and do not eat. There are only 13 species named in the world. The Pteronarcyidae is primarily a North American family, where it contains two genera and ten species; both genera and four species are reported in B.C.
Adults, measured from the front of the head to the tips of the folded wings, are usually longer than 25 mm. The anal area of the forewing has two or more rows of crossveins. Abdominal segments retain vestiges of larval gills – segments 1 and 2 in Pteronarcys and 1 to 3 in Pteronarcella. The cerci are multisegmented. The larvae are 20 to 50 mm long when mature. They have highly branched gills on the sides and undersides of all thoracic segments and gill tufts occur on the sterna of the basal abdominal segments in the pattern seen in the adults. Development may require two or three years; emergence is typically in early summer and adults live up to a month.
Pteronarcys occurs in small to large streams in eastern Asia and North America. Two species are restricted to the western mountains and occur throughout B.C., north to the Yukon – P. californica Newport and P. princeps Banks. A third species, P. dorsata (Say), ranges across the boreal forests and south in the eastern and western mountains. It is the largest stonefly on the continent -- over 60 mm from the head to the tip of the folded wings. In B.C. it lives in the larger rivers such as the Fraser. Pteronarcella is a genus of two species restricted to the western mountains of North America; P. badia (Hagen) is widespread in the southern interior of B.C., but as it ranges northwest to Alaska it probably also occurs in the northern part of the province. P. regularis (Hagen), although not recorded from B.C., probably occurs there because it is known from Alaska and Alberta as well as in states to the south.