The Odonata (Damselflies and Dragonflies)
Royal British Columbia Museum
675 Belleville Street
Victoria, B.C., V8W 9W2
Sydney G. Cannings
The Montane Cordillera Ecozone extends from the eastern Rocky Mountains in Alberta to the western slope of the Cascades in British Columbia, and from the latitude of the Skeena Mountains in northern British Columbia to the United States border. It is Canada’s sixth largest ecozone, covering more than 49 million hectares. The Montane Cordillera is probably Canada’s most complex ecozone, with landscapes ranging from alpine tundra to dense coniferous forests, riparian woodlands, grasslands and dry shrub-steppe reflecting the exceptional diversity of topography and climate (Scudder and Smith 1998).
The complex topography of the ecozone results in large differences in temperature and precipitation across the Ecozone. The plateaus in the centre of British Columbia are in the rain-shadow of the Coast Mountains and have a mean annual precipitation in some areas less than 30 cm. However in the Selkirk Mountains mean annual precipitation is 250-350 cm in some areas, with 150-250 cm in much of the Rocky Mountains. Most of interior British Columbia is strongly influenced by both continental and maritime air, the latter being more prevalent in the south. In consequence, the southern interior valleys experience winter temperatures much less rigorous than those in the north. The warmest summer temperatures are recorded in the southern interior valleys, where, in the extreme South Okanagan, the mean daily temperature in July is over 22° C (Scudder and Smith 1998).
The major early works on Odonata of the Canadian Cordillera were Walker (1912, 1925, 1927), Buckell (1938) and Whitehouse (1918a, 1918b, 1941). Walker (1953, 1958) and Walker and Corbet (1975), dealing with the dragonflies of Canada and Alaska, included some of these and other records of dragonflies in the ecozone, and added considerable ecological information. Scudder et al. (1976) and Cannings and Stuart (1977) updated and summarized the information known for British Columbia. Since then, inventories and general collecting have improved our knowledge considerably (Cannings 1980a, Cannings 1983, Cannings and Cannings 1983, Cannings 1984, Cannings and Cannings 1986, Cannings and Cannings 1994, Cannings 1998, Cannings et al. 2000). The distribution, status and ecological requirements of the fauna are well known for the Okanagan Valley, moderately known for the remaining southern valleys, Wells Gray Park and local areas on the Cariboo-Chilcotin Plateaus. The region north of 52N and all mountainous areas remain only sparsely surveyed.
Introduction to the dragonflies
The Odonata (dragonflies and damselflies) is a small order of insects of about 5000 named species in 33 families worldwide. It is predominantly tropical in distribution and is not as diverse at higher latitudes. Nevertheless, 77 species are known from the Montane Cordillera Ecozone; this is 90% of the 86 species recorded from British Columbia (there are 202 recorded in Canada). Because of the abundance and size of individuals, the order forms one of the predominant groups in standing freshwater communities in the ecozone. In the western mountains species are less abundant in running water than they are in standing water habitats. Odonates occur around most types of fresh water. Certain kinds prefer lakeshores, others are found only along streams, or around springs and in peatlands. Ponds and marshes rich in aquatic vegetation support the most species.
The Odonata and their ancestors are some of the most ancient of insects. They have many primitive features, but also possess many specializations that reflect their aerial and predatory life. The order is divided into three suborders: the Zygoptera (damselflies), the Anisoptera (dragonflies) and the Anisozygoptera, a small group of two species from Asia that is intermediate in appearance between the other two suborders. Damselflies are slimmer, often smaller, and usually fly more slowly than dragonflies. At rest their equal-sized wings are usually held together above the body. Zygoptera means "joined wings". Dragonflies are robust, often fast-flying, with the hindwings broader than the forewings; when perched they hold their wings out away from the body. Anisoptera means "unequal wings". The higher classification of the order is contentious, but the Zygoptera are usually considered the more pleisiomorphic of the two major suborders. They are viewed as a monophyletic sister group of the Anisozygoptera plus Anisoptera in recent phylogenetic studies (Carle 1982, Bechly 1995).
Metamorphosis in odonates is striking but there is no pupal stage. The aquatic larvae are predacious and are armed with an enormously enlarged, hinged labium, which is used as an extendible grasping organ for capturing prey. Larvae are voracious, eating aquatic small crustaceans and even fish. Larvae can be placed in three categories according to their feeding behaviour. Climbers (Zygoptera, Aeshnidae) are streamlined stalkers that live in submerged vegetation. Sprawlers (Macromiidae, Corduliidae and Libellulidae) lie in ambush on the bottom mud and detritus. Burrowers (Gomphidae, Cordulegastridae) cover themselves with sand and mud and await their prey. Larvae go through 10 to 15 instars before emerging as terrestrial adults.
Adults are aerial, visually oriented predators: large, strong-flying insects with large eyes, strong mandibles and spiny legs. Prey is a wide range of flying insects; these are usually captured in flight. Adults are often colourfully patterned and exhibit a wide variety of readily observed behaviour. Mature males patrol the breeding habitats, agressively searching for mates, and may, like birds, defend a territory against other males of the species. These territories limit aggression and prevent undue disturbance of egg-laying females. Sometimes in crowded situations group territories with dominance hierarchies are established.
In the damselflies and many dragonflies development is rapid. Even in the north and at higher elevations in the Montane Cordillera the life cycle takes about a year. Lestes and some Sympetrum species overwinter as diapausing eggs, hatch in the spring and emerge as adults in the summer. Others overwinter as larvae and emerge the following spring or summer, although probably in some species and conditions, the larvae overwinter two years. However, in the larger dragonflies, such as Aeshna or Somatochlora, the short summers of high altitudes and the northern parts of the zone often mean that four or five years are spent in the larval stage. Adults live for about one to two months in this region.
A systematic checklist of the 78 species (20 of which are potentially endangered, threatened or vulnerable) including their zoogeographic elements, is included as Appendix 1. A brief review of the major taxa of the ecozone with notes on habits is presented below.
ORDER ODONATA (DRAGONFLIES AND DAMSELFLIES)
SUBORDER ZYGOPTERA (DAMSELFLIES)
FAMILY CALOPTERYGIDAE (JEWELWINGS)
FAMILY LESTIDAE (SPREADWINGS)
Cannings et al. (1980) report on the ecology of three of these species that inhabit a series of lakes on the Chilcotin Plateau that range greatly in salinity and alkalinity. Lestes dryas colonized only the freshest ponds, L. disjunctus occurred in lakes up to medium salinities, and L. congener inhabited the complete range of salinities and occurred in very large numbers even at the highest concentrations (conductivity of 15524 microSiemens). Emergence and mating of the three species were also temporally separate; L. dryas emerged about ten days before L. disjunctus, which preceded L. congener by nine days. The main emergence of L. disjunctus occurred twenty days before the peak of the L. congener emergence.
L. forcipatus was discovered in the Montane Cordillera for the first time in 1998 and is now known from numerous localities in southeastern British Columbia. This species is probably more common than records indicate; it has certainly been overlooked over much of its range because of its similarilty to the common L. disjunctus.
FAMILY COENAGRIONIDAE (POND DAMSELS)
Ischnura is a cosmopolitan genus whose distribution in North America is decidedly southern in character. Two species, I. cervula and I. perparva are occur in the Montane Cordillera Ecozone, and are common in Typha and Scirpus marshes in the south; the former species ranges north to at least 53o. Coenagrion is a predominantly Palaearctic genus with three species ranging across most of boreal North America; C. interrogatum and C. resolutum occur in the ecozone. The former, the most boreal of Nearctic damselflies, is apparently restricted to water bodies with aquatic moss (Cannings and Cannings 1994). The two western Canadian species of Argia are of special interest in the Montane Cordillera. Both Argia emma and A. vivida live in streams, a rather unusual habitat for the Zygoptera of the region. A. emma also develops along lakeshores in southern valleys, and A. vivida is scattered here and there, mostly in the warm rivulets flowing from thermal springs. Both are considered threatened or vulnerable in the area. Pritchard (1982, 1989) , Conrad and Pritchard (1988, 1990) and Conrad (1992) documented the development and behaviour of A. vivida in hotsprings at Banff, Alberta.and Albert Canyon and Halcyon Hotsprings, B.C. Amphiagrion abbreviatum and Nehalennia irene are the sole representatives of their genera in the ecozone. The former is a red and black species inhabiting springs and seeps in the southern valleys; the latter is a tiny blue and metallic green denizen of sedge marshes.
FAMILY AESHNIDAE (DARNERS)
Cannings (1996) keys the species in the region and outlines the biology and distribution of the species of Aeshna. Peters (1998) discusses the ecology of some Aeshna species of British Columbia and presents a key to adults based on wings only. This allows the identification of specimens that have been eaten by birds, a situation often encountered in the field. Six of the 13 Aeshna species are boreal (A. juncea and A. subarctica are Holarctic) and four others are transcontinental in the Transition forests. Three are strictly western in range. A. subarctica, A. sitchensis, A. septentrionalis and A. tuberculifera are peatland obligates in the Montane Cordillera and are found primarily at higher elevations, at least in the south. A. tuberculifera has a very local distribution in the ecozone and is known from only a very few peatland localities; we maintain it on the list of species of management concern. A. interrupta is one of the most widespread species in the area and is found in many habitats from northern peatlands to temporary ponds. It is the characteristic species of grassland ponds. A. constricta is an uncommon species typical of small ponds in the south; its preference for habitats that are often threatened by human development place it on the vulnerable list. Along with A. tuberculifera, the females mimic males in coloration and behaviour; they are also the only species of the genus in our region that regularly lay their eggs above the water in emergent vegetation.
A. californica is remarkable for its springtime flight season. In the south, it may appear as early as the last week of April, emerging with the earliest dragonflies. A species of lowland ponds, it normally disappears by early August, just when many darner species are reaching their peak abundance. Anax junius, the Green Darner, has a southern transcontinental distribution. At least some populations appear to migrate, with spring immigrants moving north in the spring and their offspring flying south in August and September. Other populations are resident.
FAMILY PETALURIDAE (PETALTAILS)
The larva is unlike that of any of our other dragonflies -- it is amphibious. It digs an L-shaped burrow in the mud and moss saturated by the trickling spring water, with the lower, horizontal part of the burrow pointing upstream. Dozens of burrows can be concentrated in a small area. The larvae are mostly nocturnal, coming to the burrow entrance to await their prey. They can breathe air for long periods and often forage well out of the water-filled burrow. Tanypteryx is seldom seen in British Columbia (larvae have never been found in Canada) and because of its apparent rarity, we have placed it on the list of vulnerable species.
FAMILY GOMPHIDAE (CLUBTAILS)
Gomphus graslinellus lives along valley bottom lakeshores in the Okanagan, Shuswap, and Boundary regions, the only part of its Canadian range west of Manitoba. The larvae burrow in the sand and silt along wave-washed shores and the adults bask on the warm beaches. Stylurus olivaceus is closely related and has similar habits and distribution in the ecozone, although it also inhabits the larger, warm rivers such as the Okanagan and Thompson. Ophiogomphus colubrinus is a boreal species, uncommon in the northern streams of the Montane Cordillera. O. occidentis and O. severus are more widespread species that live in both lakes and streams; the former is restricted to lowland areas south of 51oN and the latter ranges well north of the ecozone into the Northwest Territories.
FAMILY CORDULEGASTRIDAE (SPIKETAILS)
FAMILY MACROMIIDAE (CRUISERS)
FAMILY CORDULIIDAE (EMERALDS)
FAMILY LIBELLULIDAE (SKIMMERS)
Leucorrhinia species are small, black, white-faced dragonflies marked with red or yellow. Five of the six species are boreal and are most prevalent in the mountains or in the north around the marshy shores of lakes in the late spring or early summer. The tiny L. patricia is rare, known from only a few peatland ponds where the larvae live in aquatic moss mats. L. intacta is the anomaly in the genus, preferring cattail marshes in warm valley bottoms. The genus Libellula contains five large, striking species in the Montane Cordillera; most have banded or spotted wings, and in most species, the males sport white, pruinose abdomens. L. quadrimaculata, one of the most widespread dragonflies on the globe, is everywhere, from northern bogs to alkaline ponds. L. pulchella, boldly patterned, lives only in the warmest parts of the southern valleys. Most of this species' habitat has been drained and filled in the past century.
Sympetrum species are mostly small red dragonflies abundant as adults in the late summer and fall. The nine species are especially common in marshy lowland habitats. Unusual in the genus, the colour of S. danae is black and yellow. This species has a wide ecological tolerance, being equally at home in mountain peatlands and lowland marshes. S. vicinum is rare in the Montane Cordillera, and therefore on the list of species of management concern. It flies late, well into November in mild autumns in the south Okanagan Valley. S. costiferum and S. corruptum are typical of saline ponds in the grasslands of the ecozone, and along with the latter, S. madidum and S. pallipes can develop in ephemeral ponds. Cannings (1980b, 1981) described the larva and the ecological preferences of S. madidum on the Chilcotin plateau.
Erythemis collocata is the rarest of all the species in the Ecozone, known only from the old oxbows of the Okanagan River near the north end of Osoyoos Lake at the southern end of the Okanagan Valley.
Zoogeography and Faunal Elements
Species may be grouped with others that share similar distributions to form what can be termed faunal elements. The majority of the 77 species known from the Montane Cordillera Ecozone are restricted to the Nearctic region, although six are holarctic (defined here as species with transcontinental ranges in both North America and Eurasia). Two species (Anax junius and Sympetrum corruptum) are known from eastern Asia but do not have holarctic distributions. This section describes the Nearctic faunal elements pertaining to the ecozone (species with holarctic distributions are also assigned to a North American faunal element).
The faunal elements are thus represented in the Montane Cordillera Ecozone as follows:
Twenty-five species of Boreal origin (32%) are recorded. Of these, 13 (17%) are Widespread Boreal, 7 (9%) are Southern Boreal, 4 (5%) are Northern Boreal and 2 (3%) are Western Boreal. Transition species total 17 species (22%) and there are 13 (XX20%) Cordilleran species. Nine species (1XX0%) are Western, 6 (9%) are Austral and 6(XX7%) are Widespread according to our definitions.
Six species -- Lestes dryas, Enallagma cyathigerum, Aeshna juncea, A. subarctica, Libellula quadrimaculata, and Sympetrum danae -- are holarctic, ranging around the Northern Hemisphere. It is most likely that these species have had such wide distributions since before the last glacial age. In contrast to the situation in some other insect groups, there is no evidence that the Beringian glacial refugium influenced the distribution of Montane Cordilleran Odonata. The only odonate with a Beringian distribution, Somatochlora sahlbergi Tryböm, does not range south of the central Yukon (Cannings and Cannings 1997). There, however, it hybridizes with two congeners widespread in the Montane Cordillera: S. albicincta and S. hudsonica (Cannings and Cannings 1985).
Farther north in the Cordillera, 70 percent of 33 species in the Yukon are of Boreal origin (Cannings and Cannings 1997); in the Montane Cordillera this boreal component is reduced to 34 percent. This reduction is the result of the strong influence of more southerly faunas, since all but one (Somatochlora kennedyi Walker) of the Yukon’s boreal species range south into the Montane Cordillera. Nineteen species in the Boreal element of the Montane Cordillera range south of 51oN along the mountains and plateaus of the Cordillera: Coenagrion resolutum, Enallagma boreale, E. cyathigerum, Nehalennia irene, Aeshna eremita, A. interrupta, A. juncea, A. sitchensis, A. subarctica, Cordulia shurtleffi, Somatochlora albicincta, S. cingulata, S. hudsonica, S. minor, S. walshii, Leucorrhinia borealis, L. hudsonica, L. proxima, and Sympetrum danae. These also could be termed boreomontane species. In contrast, six species of the Boreal element are rare as far south as even the northern parts of the Montane Cordillera: Coenagrion interrogatum, Aeshna septentrionalis, Ophiogomphus colubrinus, Somatochlora septentrionalis, S. whitehousei, and Leucorrhinia patricia. Except for Aeshna septentrionalis, these species are also sparsely distributed further to the north relative to their numbers east of the Cordillera. Their rarity in the west is probably more related to habitat scarcity rather than to limited post-glacial colonization.
Since the last glacial age, the Montane Cordillera has been recolonized by Odonata from at least two southern refugia: one in what is now the southeastern United States and another in the intermontane Cordillera south of Canada. The putative species pairs Somatochlora albicincta/ S. hudsonica and Leucorrhinia hudsonica/ L. borealis have distribution patterns that suggest this history. S. albicincta and L. hudsonica are boreal species with transcontinental ranges. Presumably they inhabited the southeastern refugium and recolonized the Montane Cordillera from the east and north, following the early retreat of the continental ice sheet east of the Rocky Mountains. S. hudsonica and L. borealis have similar distributions but do not range east of Hudson’s Bay, indicating that they recolonized the Cordillera from the south.
The Cypress Hills of southeastern Alberta and southwestern Saskatchewan are, for many species from diverse groups, an outlier of the Montane Cordillera. The upper plateau of the Cypress Hills was never glaciated and the surrounding territory became free of ice very early. The forested hills were soon repopulated by western montane taxa, rather than taxa from the eastern boreal forests. Lodgepole pine (Pinus contorta), Northern (Red-shafted) Flicker (Colaptes auratus cafer), Townsend's Warbler (Dendroica townsendi) The Cordilleran Odonata are represented there by Aeshna palmata.
From 10,000 to 8,000 years before present, following the retreat of the Cordilleran glaciers, the climate became warmer in the ecozone than it is today (Hebda 1995). Presumably, although there is no fossil evidence, southern, warm-adapted species ranged more widely to the north than they do at present. Disjunct, present-day populations in isolated, unusually warm habitats offer evidence for these former distributions. For example, Ischnura damula is now restricted in the Cordillera to the Liard River Hot Springs in the Boreal Cordillera Ecozone; further east and south, its nearest population is in southern Saskatchewan. Argia vivida, in a genus known for its Neotropical origins (Pritchard 1991), is largely associated with geothermally heated streams in the ecozone (Pritchard 1982). It, too, perhaps, was more widespread during the warmer hypsithermal period and has subsequently been restricted to warm sites (Pritchard 1989).
Patterns of distribution between the Pacific Maritime and the Montane Cordillera ecozones require more study. In Washington State, several species considered completely coastal in British Columbia, such as Ishnura erratica, Sympetrum illotum and Pachydiplax longipennis, also occur east of the Cascade Mountains. The Columbia River Valley may have acted as a corridor for these coastal species to range inland. In addition, a number of interior species such as Archilestes californica McLachlan, Erpetogomphus compositus Hagen, and Gomphus lynnae Paulson do not range north of the Columbia Basin in central Washington. This area is the northern limit of distribution of many plants and animals. In contrast, Argia emma is locally common in the lower Fraser River Valley of British Columbia on the western side of the Coast Mountains. It has apparently colonized this area by using the Fraser River Valley as a conduit from the Interior valleys of the Montane Cordillera Ecozone. It is not known from coastal habitats in Washington State, although it is common east of the Cascades.
Dragonfly Habitat in The Montane Cordillera
The general aquatic habitats available to dragonflies in the Ecozone are listed below, with the distinctive species associated with each.
Analysis of trends in species occurrence and abundance
Draining of wetlands
Flooding of wetlands
Hundreds of smaller, high elevation dams built to supply water to lowland communities have flooded peatlands, ponds, shallow lakes and slow streams, creating larger lake habitat and causing a reduction in odonate diversity. This habitat loss has eliminated populations of dragonflies such as Coenagrion interrogatum, Aeshna sitchensis, A. subarctica, Somatochlora minor, S. franklini, and many others and, assuming shorelines lack extensive marshy or peatland edges, replaced them with a few species characteristic of montane lakeshores: Aeshna eremita, Aeshna umbrosa, and Somatochlora albicincta.
The aquatic communities of many systems that historically contained fish have also been altered by the purposeful or accidental introduction of non-native fish species. In the Columbia watershed, 16 species, a full 37 percent of the entire fish fauna, are introduced. Some of these species not only eat many odonate larvae, but also alter the habitat structure. Carp (Carpinus carpio) were introduced into the mainstem lakes of the Okanagan in 1917 and subsequently destroyed or reduced much of the native aquatic vegetation, including Lemna and Potamogeton (Brooks 1973).
Hot springs development
Recommendations for Future Inventory, Research and Monitoring
Odonata inventory in the Montane Cordillera has been extensive but not systematic. Even in the southern valleys, much more work is necessary. A comprehensive inventory in 1997 in the Okanagan basin (the best collected area in the zone) greatly increased our knowledge of the abundance and distribution of many species (Cannings 1998). In doing so, however, it revealed how much additional effort is needed to give a more precise idea of dragonfly distribution throughout the zone. For example, the known range of Coenagrion interrogatum was extended from Heckman Pass, Tweedsmuir Park, on the extreme western boundary of the Ecozone south to the Okanagan Highlands; four localities for the species were discovered in the Okanagan. It is clear that the distribution of this species in the zone remains poorly known. The number of localities for some uncommon lowland species was also increased significantly; for example, Argia vivida localities increased from three to eight and Argia emma from five to 16.
An inventory in the Columbia-Kootenay region in 1998-99 (Cannings et al. 2000) increased the species list for the southeastern part of the ecozone from 57to 66 and added three species new to British Columbia (Calopteryx aequabilis, Lestes forcipatus and Somatochlora forcipata). The ranges of several other species ( including Coenagrion interrogatum, Cordulegaster dorsalis, Gomphus graslinellus, and Sympetrum vicinum were significantly extended into the southeastern part of the province.
Outside the Okanagan drainage (Cannings 1998), the Kootenays (Cannings et al. 2000) and Becher's Prairie on the Chilcotin Plateau (Cannings and Cannings 1987), no formal inventories have been made anywhere in the zone. High priorities for future inventories are the species-rich, lowland valleys of the Kootenay and Thompson regions. For clarifying the ranges of northern species, intensive work in the Cariboo, Omineca, Selkirk, Purcell and Rocky Mountains; the Bulkley Valley, and the Babine Upland is critical.
A few species are known from adjacent areas and may occur within the zone. Tramea lacerata, Pantala hymenaea, and P. flavescens, all well known for their wide-ranging flights, are recorded from central Washington State; the first two have been recorded as wanderers on the south coast of British Columbia (Cannings 1988, 1997). To the north, Somatochlora kennedyi is known from the Taiga Plains in northeastern British Columbia and from the Boreal Cordillera in extreme southern Yukon, and is almost certain to occur at the northern limits of the Montane Cordillera Ecozone.
Increased inventory efforts would especially improve our knowledge of the species that range widely across the zone but are known from few localities: for example, Lestes forcipatus, Aeshna tuberculifera, A. septentrionalis, Ophiogomphus colubrinus, Cordulegaster dorsalis, Somatochlora cingulata, S. septentrionalis, and Leucorrhinia patricia. Other species, such as Calopteryx aequabilis, are known from only one locality within the ecozone and their status needs to be elucidated. West of Manitoba, Somatochlora forcipata is known from only four sites, including one in Banff National Park (Walker and Corbet 1975). In the Montane Cordillera, Enallagma civile is recorded only from Bridge Lake in south-central British Columbia; otherwise it is not known west of Swift Current, Saskatchewan (Cannings and Stuart 1977). The extent of the range of Tanypteryx hageni along the mountains at the southwestern edge of the zone needs to be studied.
No studies examining the effects of human activity in the environment (e.g. siltation and elevated temperatures in streams in logged areas or the effect of dams on dragonfly populations) have been undertaken in the ecozone, and no long-term monitoring studies are in place that could detect changes in species composition and abundance of dragonfly populations. Although recent inventories have increased our knowledge of the habitat requirements of a number of species, our understanding of the needs of most species remains rudimentary, and more ecological studies would be of enormous benefit.
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Appendix 1: Checklist of Montane Cordillera Odonata -- 77 species
FAMILY CALOPTERYGIDAE (JEWELWINGS) (1 species)
FAMILY LESTIDAE (SPREADWINGS) (4 species)
FAMILY COENAGRIONIDAE (POND DAMSELS) (15 species)
FAMILY AESHNIDAE (DARNERS) (14 species)
FAMILY PETALURIDAE (PETALTAILS) (1 species)
FAMILY GOMPHIDAE (CLUBTAILS) (5 species)
FAMILY CORDULEGASTRIDAE (SPIKETAILS) (1 species)
FAMILY MACROMIIDAE (CRUISERS) (1 species)
FAMILY CORDULIIDAE (EMERALDS) (13 species)
FAMILY LIBELLULIDAE (SKIMMERS) (21 species)
by Robert A. and Sydney G. Cannings
What are Dragonflies and Damselflies?
Dragonflies and damselflies, in the Order Odonata, are some of the most ancient of insects. They have many primitive features, but also possess many specializations that reflect their aerial and predatory life. Damselflies are slimmer, often smaller, and usually fly more slowly than dragonflies. At rest their equal-sized wings are usually held together above the body. Dragonflies are robust, often fast-flying, with the hindwings broader than the forewings; when perched they hold their wings out away from the body. Metamorphosis in odonates is striking but there is no pupal stage. The aquatic larvae are predacious and are armed with an enormously enlarged, hinged labium, which is used as an extendible grasping organ for capturing prey. Larvae are voracious, eating aquatic small crustaceans and even fish. Adults are aerial, visually oriented predators: large, strong-flying insects with large eyes, strong mandibles and spiny legs.
Where do I find Dragonflies and Damselflies?
Dragonflies and damselflies are aquatic insects. The larvae live in ponds, marshes, peatlands, streams and lakes. Climbers (e.g., damselflies, darners) are streamlined stalkers that live in submerged vegetation. Sprawlers (river cruisers, emeralds, and skimmers) lie in ambush on the bottom mud and detritus. Burrowers (clubtails, spiketails) cover themselves with sand and mud on the bottom and ambush their prey.
Adults can spend much of the time away from water, hunting their insect prey in sunny, open areas. When they are ready to breed, they return to the water. There, males patrol the breeding habitats, agressively searching for mates, and may, like birds, defend a territory against other males of the species. Females visit the breeding area periodically to mate and lay eggs. Because they are drawn to the breeding sites, and because they are easy to watch there, these places are ideal for dragonfly study.
What is the Dragonfly and Damselfly species diversity of the Montane Cordillera Ecozone?
What species are at risk?
Twenty species are considered rare, based on collections in museums. However, with increased collecting, some of these (e.g. the Sweetflag Spreadwing (Lestes forcipatus), the Black-tipped Darner (Aeshna tuberculifera) and the Lake Emerald (Somatochlora cingulata)) will turn out to be more widespread than we once believed. Others, such as the Vivid Dancer (Argia vivida) live in restricted habitats that are threatened by human-caused development and so are more likely to be at risk, even if more populations are discovered.
What are the human impacts on Dragonflies and Damselflies?
The greatest impacts are the destruction and degradation of the aquatic habitats of dragonflies, especially by draining and filling. These changes have eliminated populations of almost all dragonfly species on the ecozone list. Large hydroelectric and flood control dams not only inundate wetlands, lakes and streams upstream but completely alter the natural flow regime downstream. Hundreds of smaller, high elevation dams built to supply water to lowland communities have flooded peatlands, ponds, shallow lakes and slow streams, creating larger lake habitat and causing a reduction in odonate diversity. Other negative affects come from the introduction of fish into originally fish-free lakes, destruction of natural lakeshores, disturbance of fragile pond and stream habitats by livestock, and the siltation and temperature increases in streams caused by logging and associated road building.
Trends in dragonfly populations
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