Damselflies and dragonflies

Code QO999999

See Key to Families of Australian Aquatic Odonate Larvae

A small order of conspicuous insects, comprising a few thousand species, with about one-third belonging to suborder Zygoptera (damselflies), two-thirds to suborder Anisoptera (dragonflies) and 2 Oriental species in a third suborder Anisozygoptera. Adult medium to large (from <2 - >15 cm long); mobile head with large, multi-faceted compound eyes and 3 ocelli, short antennae and mandibulate mouthparts; enlarged thorax to accommodate flight muscles of 2 pairs of elongate membranous wings; slender 10-segmented abdomen. Zygopteran adult with widely separated eyes and fore and hind wings equal in shape with narrow bases; anisopteran adult with eyes either contiguous or slightly to widely separated, wings with characteristic closed cells called triangle (T) and hypertriangle (ht) and hind wings considerably wider at base than fore wings.

Larvae with variable number of up to 15 aquatic instars; fully developed mandibulate mouthparts, including extensible, grasping labium or "mask'; developing wings visible in older nymphs; closed tracheal system lacking spiracles, but specialised gas exchange surfaces present on abdomen as external gills (Zygoptera) or internal folds in rectum (Anisoptera). Zygopteran larva slender, with head wider than thorax and apex of abdomen with 3 (rarely 2) elongate tracheal gills (caudal lamellae); anisopteran more stoutly built with head rarely much broader than thorax, and abdominal apex characterised by anal pyramid consisting of 3 short projections and a pair of cerci.

Nymphs are predatory on other aquatic organisms. Adult predatory on terrestrial, aerial prey. At metamorphosis, the pharate adult moves to water/land surface where atmospheric gaseous exchange commences and then it crawls from water, anchors terrestrially and imago emerges from cuticle of final-instar larva; imago long-lived, active aerial. Larvae occur in all waterbodies, particularly well-oxygenated, standing waters, but elevated temperatures, organic enrichment or increased sediment loads are tolerated by many species.