Introduction The order Odonata is separated into three suborders: Anisoptera, the dragonflies, Zygoptera, the damselflies, and Anisozygoptera (found in Nepal and Japan-the body being anisopteran-like and the wings zygopteran-like). Adults and larvae of Anisoptera and Zygoptera are readily distinguishable (Figs. 34.1 and 34.2). For most people, adult dragonflies are probably the most recognizable of all hemimetabolous aquatic insects. They are strong fliers, and we have probably all seen these large insects flying about and feeding on insects in our backyards.
General Features, Life Cycle There are over 5000 species of extant odonates world-wide-all aquatic in the larval stage, except for a few non-North American species living in damp leaf litter. About 650 species in 11 families are found in North America (seven families of Anisoptera and four families of Zygoptera). In Alberta, there are four families of Anisoptera (Aeshnidae, Gomphidae, Libellulidae, and Corduliidae), representing at least 10 genera and about 50 species. Some larvae of the four families are show in Figures 34.A through 34.K and Plate 34.1. Representatives of the three families of Zygoptera (Calopterygidae, Lestidae, and Coenagrionidae) found in Alberta are shown in Fig 34.L. through Fig 34.O and Plate 34.1. In Alberta, there are only about 23 zygopteran species in 8 genera.
Larvae of the four dragonfly families appear to be widely distributed throughout the province, although rarely found in large numbers. For damselflies, Coenagrionidae larvae are abundant throughout much of Alberta, Lestidae larvae less so, but widely distributed, and Calopterygidae larvae appear to be restricted to northeastern Alberta, in streams of the Beaver River drainage.
Dragonfly and damselfly larvae are predacious, capturing other aquatic invertebrates with the large labium. Most odonate larvae probably have 10 or more larval instars; for example the damselfly Argia vivida Hagen, which lives in geothermal streams of the Banff, Alberta, area had 11, 12, or 13 larval molts when studied in the laboratory (Leggott and Pritchard 1985a, 1985b).
When the larva is ready to transform into the adult, it leaves the water and transforms holding on to perhaps the first suitable terrestrial surface encountered, e.g. stems of higher aquatic plants or even a tree trunk. Shortly after transforming, adults will be seen flying and feeding on other flying insects, the adults also being predacious. Adults, especially dragonflies, can fly considerable distances from where they emerged. Eventually the adults will fly back to an aquatic habitat. The adult male will then usually patrol a stretch of pond or stream looking for a female. The male will seize the female while both are in flight and the two, in tandem, will eventually land on some terrestrial surface, where mating takes place.
Fertilized eggs will usually be deposited shortly after copulation. For most dragonflies, the female, often still in tandem with the male, dips to the surface of the water and release a few eggs at a time. However, Aeshnidae females and all damselfly females, using an ovipositor, insert fertilized eggs into stems of aquatic plants. Epitheca females (Corduliidae) lay eggs in a mass of jelly often communally (Cannings 1988). Females of all damselflies also insert the fertilized eggs into stems of aquatic plants. Probably most damselflies have one generation a year in Alberta. For example, in a boreal forest pond in west central Alberta, Lestes disjunctus (Lestidae) had a univoltine cycle, with adults present in July and August and the population overwintering in the egg stage; in contrast, Coenagrion resolutum in the same pond could be either univoltine or have a two-year cycle-in both cases, adults were on the wing in June and July and the populations overwintered in the larval stage (Baker and Clifford 1981). Some dragonflies also have one-year cycles, but many have two to four and perhaps even five year cycles.
Collecting, Identifying, Preserving Most dragonfly and damselfly larvae are found in small standing water habitats, such as small ponds and marshes. A few species are found in the shallow regions of large lakes, and they are not uncommon in some streams, especially slow-moving ones. Most Alberta genera are found in both running and standing waters, although Ophiogomphus and Calopteryx appear to be restricted to streams. A pond-net is suitable for sampling most odonates. Many larvae are burrowers, and raking up the substrata will collect some of these; others are climbers, especially on aquatic plants, and such plants should be examined directly or placed in a white pan until the larvae (and other invertebrates) crawl out of the vegetation. Larvae can be preserved in 70-75% ethanol. It is a good procedure to pierce the exoskeleton of the big aeshnids so that the preservative will be more effective on the internal tissues.
Alberta's Fauna and Pictorial Keys The pictorial keys follow mainly diagnostic features given in Walker (1953), (1958) and Walker and Corbet (1975). The zygopteran key is modified from one originally constructed by Robert L. Baker, University of Alberta. For anisopterans, separating Aeshna and Anax larvae can be difficult; it is also difficult to separate the zygopterans Coenagrion, Enallagma and Ischnura. For keys to all North American genera, see Walker (1953), (1958) and Walker and Corbet (1975).
Genera Species of the genera listed below have been reported from Alberta.
- Suborder Anisoptera (dragonflies)
- Family Aeshnidae
- Family Corduliidae
- Cordulia, Epitheca, Somatochlora
- Family Gomphidae
- Family Libellulidae
- Leucorrhinia, Libellula, Pachydiplax (doubtful), Sympetrum
- Suborder Zygoptera (damselflies)
- Family Calopterygidae
- Calopteryx
- Family Coenagrionidae
- Argia, Amphiagrion, Nehalennia, Coenagrion, Enallagma, Ischnura
- Family Lestidae
Some Taxa Not Reported From Alberta Anisoptera—Three North American dragonfly families have not been reported from Alberta: Cordulegastridae (see ODONATA pictorial keys), Macromiidae (see pictorial keys) and Petaluridae, although one petalurid genus, Tanypteryx, is found in British Columbia. Cordulegastridae larvae bury themselves in sand and silt at the bottom of small streams. One genus, Cordulegaster, is found in British Columbia. Larvae of Macromiidae live in large streams and lakes, and have long, spider-like legs. Petaluridae larvae would key to Aeshnidae in the ODONATA pictorial key. In contrast to aeshnids, petalurid larvae have short, stout and very hairy antennal articles; in fact the whole larva is hairy. Their dirty appearance, when collected, is associated with their unusual habitat. Larvae burrow into soil of mosses that are bathed by a shallow stream of water (Walker and Corbet 1975).
Zygoptera—There is one damselfly family found in North America north of Mexico that is not found in Alberta; this is Protoneuridae, but specimens have been collected only as far north as Texas.
Survey of References The following references pertain to Alberta's odonates: Acorn (1983), Baker (1980, 1981 a, 1981 b, 1981 c, 1982), Baker and Clifford (1980, 1981, 1982), Cannings (1980a, 1980b), Cannings and Cannings (1983), Conrad (1987), Conrad and Pritchard (1988, 1989), Daborn (1969, 1971), Hilton (1985), Leggott (1984), Leggott and Pritchard (1985a, 1985b, 1986), Musbach (1977), Prtichard (1963, 1964a, 1964b, 1965a, 1965b, 1966, 1971, 1976a, 1980b, 1982a, 1986, 1988), Pritchard and Leggott (1987), Pritchard and Pelchat (1977), Reist (1980), Rosenberg (1972, 1975b), Whitehouse (1917, 191 8a, 1918b). See also the bottom fauna references listed at the end of Chapter 3 (Porifera).
For anatomical features important in identifying dragonfly and damselfly larvae, see Figure 34.1 and Figure 34.2.
Pictorial Keys
Figures
Figure 34.1
- A dragonfly larva (Anisoptera).
Figure 34.2
- A damselfly larva (Zygoptera).
Figure 34.A
Figure 34.B
- Ophiogomphus sp. (Gomphidae) [25 mm]
Figure 34.C
- Gomphus sp. - immature (Gomphidae) [15 mm]
Figure 34.D
- Epitheca sp. (Corduliidae) [20 mm]
Figure 34.E
- Epitheca canis (Corduliidae) [20 mm]
Figure 34.F
- Epitheca spinigera (Corduliidae) [20 mm]
Figure 34.G
- Somatochlora hudsonica (Corduliidae) [25 mm]
Figure 34.H
- Cordulia shurtleffi (Corduliidae) [2 0mm]
Figure 34.I
- Leucorrhinia borealis -dorsal and ventral (Libellulidae) [20 mm]
Figure 34.J
- Libellula sp. (Libellulidae) [25 mm]
Figure 34.K
- Leucorrhinia sp. (Libellulidae) [20 mm]
Figure 34.L
- Calopteryx sp. (Calopterygidae) [35 mm]
Figure 34.M
- Lestes sp. (Lestidae) [20 mm]
Figure 34.N
- Argia vivida (Coenagrionidae)
Figure 34.O
- Coenagrion sp. (Coenagrionidae) [15 mm]
Plate 34.1
- Upper left: Calopteryx aequabile (Calopterydidae) [35 mm].
Upper right: Lestes sp. (Lestidae) [20 mm].
Middle right: Enallagma sp. (Coenagrionidae) [25 mm].
Lower, left to right: Ophiogomphus sp. (Gomphidae) [25 mm], Aeshna sp. (Aeshnidae) [40 mm], Epitheca sp. (Corduliidae) [20 mm];.
