All About Aquatic Insect

About 80% of all described species of animals are insects. Most are entirely terrestrial, with less than 5% of insect species having an aquatic stage. People concerned with the evolution of aquatic insects suggest most, if not all aquatic, groups descend from terrestrial insects. Although less than 5% of insects are aquatic, this still represents a very large number of species. In Alberta, there are over 90 families of aquatic insects in 11 orders. See KEY TO MAJOR AQUATIC ARTHROPOD TAXA AND ORDERS OF AQUATIC INSECTS OF ALBERTA.

     Development Insects, as true for other arthropods, grow by going through a series of molts, at which time the exoskeleton is shed. The period between molts is called an instar. Certain aquatic insects have a fixed number of instars, e.g. most caddisflies (Trichoptera) have five larval instars, a pupal instar and the adult instar. Other insect taxa can have a variable number of instars. In some insects, such as Collembola, external and internal changes during the various instars appear almost imperceptible; these insects are said to have no metamorphosis, or to be ametabolous. In most insects, however, there is a definite metamorphosis. Some insects show only a gradual change in features during the various instars including the adult instar, a condition called gradual metamorphosis or paurometaboly; the only aquatic paurometabolous insect order is Hemiptera. Some insects, having external wing buds, show a gradual change in structure during each instar until the last molt, when pronounced changes take place and result in a winged terrestrial adult. This is called incomplete metamorphosis, or hemimetabolous development. The hemimetabolous aquatic insect orders are Ephemeroptera, Plecoptera, and Odonata. The remaining aquatic insect orders exhibit complete metamorphosis, or holometabolous development. For these aquatic insects, a pupal stage is inserted between the aquatic larval stage (in which the wing buds are not obvious) and the terrestrial adult stage. The pupa can be either terrestrial or aquatic, depending on the group in question. The holometabolous insects encompass most of the aquatic insects, and in Alberta includes aquatic representatives of: Neuroptera, Megaloptera, Lepidoptera, Trichoptera, Coleoptera, and Diptera. Related to development is the use of the terms nymph and larva. In the past, many North American workers have used the word nymph instead of naiad or larva to describe the nonadult stages of the paurometabolous and hemimetabolous insects, and larva to describe the nonpupal, nonadult stages of the holometabolous insects. But for several years there has been an increasing tendency to use the word larva to describe all nonadult, nonpupal stages of immature aquatic insects, a system the German workers have used for many years. Adding to the confusion is the French usage of the word nymph for the pupal stage. It certainly would appear that larva is the preferred word by most workers today to describe all immature stages, regardless of type of development. And the term larva (with some trepidation) is used in this guide. For a historical review and opinions by numerous workers on the use of the terms larva and nymph in entomology, see Transactions of the Society for British Entomology, Volume 13, part 2, February 1958, pages 17-36. Collecting, Preserving Most aquatic insects can be collected with various types of net samplers and dredges. Fixing the sample in the field with about 80% ethanol and eventually preserving the specimens in about 75% ethanol are satisfactory procedures for most aquatic insects. Special collecting and preserving techniques will be briefly discussed for taxa where special treatment is required. Orders and Families of Alberta's Aquatic Insects

• Order Collembolaspringtails 

 Families: Poduridae and Sminthuridae 

• Order Ephemeropteramayflies 

 Families: Ametropodidae, Baetidae, Baetiscidae, Caenidae, Ephemerellidae, Ephemeridae, Heptageniidae, Leptophlebiidae, Metretopodidae, Oligoneuriidae, Polymitarcyidae, Siphlonuridae, Tricorythidae 

• Order Odonata 

o Suborder Anisopteradragonflies 

 Families: Aeshnidae, Corduliidae, Gomphidae, Libellulidae 

o Suborder Zygoptera-damselflies 

 Families: Calopterygidae, Coenagrionidae, Lestidae 

• Order Plecopterastoneflies

 Families: Capniidae, Chloroperlidae, Leuctridae, Nemouridae, Peltoperlidae, Perlidae, Perlodidae, Pteronarcyidae, Taeniopterygidae 

• Order Hemipteratrue bugs 

 Families: Belostomatidae giant water bugs, Corixidae water boatmen, Gerridaewater striders, Hebridaevelvet water bugs, Mesoveliidaewater treaders, Notonectidaeback swimmers, Saldidaeshore bugs, Veliidaebroad-shouldered water striders 

• Order Megaloptera 

 Family: Sialidaefishflies

 Order Neuroptera 

 Family: Sisyridaespongilla-flies 

 Order Lepidoptera 

 Order Trichopteracaddisflies 

 Families: Brachycentridae, Glossosomatidae, Helicopsychidae, Hydropsychidae, Hydroptilidae, Lepidostomatidae, Leptoceridae, Limnephilidae, Molannidae, Philopotamidae, Phryganeidae, Polycentropodidae, Psychomyiidae, Rhyacophilidae, Uenoidae 

 Order Coleopterabeetles 

 Families: Amphizoidaetrout stream beetles, Chrysomelidaeleaf beetles, Curculionidaeweevils, Dryopidaelong-toed water beetles, Dytiscidaepredacious water beetles, Elmidaeriffle beetles, Gyrinidaewhirligig beetles, Haliplidaecrawling water beetles, Hydraenidaeminute moss beetles, Hydrophilidaewater scavenger beetles, Lampyridaefireflies and relatives, Limnichidaemarsh-loving beetles, Scirtidaemarsh beetles 

 Order Diptera 

 Suborder Nematocera: larval head capsule usually well-developed and usually not retractable into thorax; mandibles moving in a horizontal or oblique plane. 

 Families: Blephariceridae (net-winged midges), Ceratopogonidae (=Heleidae) (biting midges), Chaoboridae (phantom midges), Chironomidae (=Tendipedidae) (midges), Culicidae (mosquitos), Deuterophlebiidae (mountain midges), Dixidae (dixid midges), Nymphomyiidae (not reported from Alberta), Psychodidae (moth flies), Ptychopteridae (=Liriopeidae) (phantom crane flies), Simuliidae (black flies),Tanyderidae (primitive crane flies), Thaumaleidae (solitary midges),Tipulidae (crane flies) 

 Suborder Brachycera: larval head capsule not well-developed, either inconspicuous or vestigial; head rudiment usually retractable into thorax. 

 (Division Orthorrhapha: head capsule incomplete and with vertical-biting mandibles.) 

 Families: Athericidae (=Rhagionidae) (snipe flies), Dolichopodidae (longlegged flies), Empididae (dance flies), Pelecorhynchidae (aquatic specimens not reported from Alberta), Stratiomyidae (soldier flies), Tabanidae (deer flies and horse flies) 

 (Division Cyclorrhapha: head capsule vestigial; no mandibles.) 

 Families: Anthomyiidae, Dryomyzidae (aquatic specimens not reported from Alberta), Ephydridae (shore flies, or brine flies), Phoridae (humpbacked flies, aquatic larvae not reported from Alberta), Sarcophagidae (flesh flies, aquatic larvae not reported from Alberta), Scatophagidae (dung flies, aquatic larvae may occur in Alberta, but the family is not treated in the DIPTERApictorial keys), Sciomyzidae (marsh flies), Syrphidae (flower flies)