Robert A. Cannings and Cannings, Sydney G. 1998. Odonata (Damselflies and Dragonflies) in Smith, I.M., and G.G.E. Scudder, eds. Assessment of species diversity in the Montane Cordillera Ecozone. Burlington: Ecological Monitoring and Assessment Network, 1998.

ODONATA
(DAMSELFLIES AND DRAGONFLIES)

Robert A. Cannings
Royal British Columbia Museum
P.O. Box 9815, Stn. Prov. Govt.
Victoria, B.C.
V8W 9W2
and
Sydney G. Cannings
Conservation Data Centre
B.C. Ministry of Environment, Lands and Parks
P.O. Box 9344, Stn. Prov. Govt.
Victoria, B.C.
V8W 9M1

INTRODUCTION

The Odonata (dragonflies and damselflies) is a small order of insects of about 5000 named species and 23 families worldwide. It is predominantly tropical in distribution and is not as diverse at higher latitudes. Nevertheless, 76 species are known from the Montane Cordillera Ecozone; this is 92% of the 83 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).

agile flight  predatory life  hold wings out

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.

voracious  damselfly larva

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.

mating

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.

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). 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 52·N and all mountainous areas remain only sparsely surveyed.

 

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