SK Aquatic "Bug" Guide

A picture guide to Saskatchewan aquatic "bugs"

This is an introductory picture guide to the Saskatchewan aquatic "bug" groups.

A downloadable version of the SK Aquatic Bug Guide is available here (SK Aquatic Bug Guide pdf (2.9 meg))

Many of the major groups of "bugs" can easily be identified with the naked eye. Even some species can be identified because they are so distinctive. Unfortunately other groups, such as the non-biting midges or bloodworms (Chironomidae: Diptera), are extremely difficult and require special techniques and a good microscope to identify them below the family level.

Most formal identifications of bugs, and other animals and plants, involve the use of dichotomous taxonomic keys where choices are made between two character states, such as legs are black, or, legs are white. However, these are often long and drawn out documents that are hard to follow even for experienced users. A simpler way to identify the basic groups is to use a "Peterson's Guide" approach which uses pictures to aid the identification process.

For this bug guide once the bug is identified the reader can click on navigation links on the left to go to a more detailed account of the group.

Freshwater Sponges (Porifera)

In clean standing or slowly flowing water, sticks and rocks may appear to have yellowish green globs on them. Often these are algae but sometimes they are sponges. Close examination will reveal some holes in the surface and possibly a spongilla fly larva. Under magnifications of 200 times or more the various supporting structures (megascleres) can be seen.

sponge body sponge megascleres
Hydra (Cnidaria, Hydrozoa)

The body of a Hydra is usually less than 20 mm long when fully extended. But when contracted it can shrink just a few mm. Most are coloured a somewhat translucent white to reddish brown although some are green due algal cells in the body wall. For these reasons they are easily overlooked in their natural habitat unless the debris is examined carefully. They can sometimes be seen hanging from the water film. Hydra consist of an elongated baglike "body" from which about six or so tentacles emerge from around a dome shaped mouth region. Hydra can be found in all types of freshwater from roadside ditchs and sloughs to sheltered microhabitats in relatively fast flowing streams. They feed on small insect larvae and crustaceans which they capture using their long tentacles that are covered with cells (nematocysts) which eject threads to entangle the prey and others that sting the prey into submission. The tentacles then pull the prey to the mouth where it is engulfed. Often there will be "buds" of smaller hydra growing out of the body. This is a form of asexual reproduction.

sponge body sponge body

In fresh samples they can be seen as small white to clear threads about 1 cm long moving in their typical thrashing pattern. They can be found anywhere in aquatic systems but are especially abundant in soft sediments with high organic content in both running and standing waters.

Aquatic Worms (Oligochaeta)

These worms are kin to the terrestrial earthworms. They are usually found in the bottom sediments of both running and standing waters. Many are bright red when alive. Most specimens are less than 2 cm long. Some species especially in the Tubifex can occur in large numbers in areas of high organic pollution such as sewage outflows and lagoons. Identification for most requires mounting on slides and examining the patterns, numbers and types of setae (chaetae)

Oligochaeta Oligochaeta Oligochaeta
Leeches (Hirudinea)

Leeches are easily recognised by their worm-like bodies with numerous segments. Size can range from 10 mm to 100 mm or more.

Snails, Limpets and Clams
(Mollusca: Gastropoda & Pelecypoda)

Snails (Gastropoda) have a coiled shell that has a spire or a simple flat coil like a rope. The "common pond snails" have the opening to the right when the spire is up. "Tadpole snails" have the opening on the left. Some families have a circular piece of shell, the operculum, which they can close the opening of the shell with.

Tadpole snail Pond Snail

Limpets (Gastropoda) have the shell in the shape of a low cone.


Clams (Pelecypoda) have two shells. Size ranges from a couple of mm across for the small "pea clams" (Family Sphaeridae) to over 15 cm for some of the larger types of "floaters" and "heal splitters".

Pea Clam Pea Clam Clam
Acari (Water Mites)

Water mites are often seen clumsily swimming or crawling amongst the water vegetation and debris. They have eight legs as adults and many are bright red in colour. Most are tiny, the largest only reaching about 2 mm in diameter. They are parasitic on other aquatic insects and can be seen attached to the insect's bodies where they suck body fluids.

Crayfish, Scuds, Tadpole Shrimps, etc

Crayfish (Decapoda) are lobster-like. They can often be seen scuttling between the rocks of slow moving streams and rivers or in the shallows of lakes. Only one species, Orconectes virilis (Hagen) occurs naturally in SK. Other species may have been introduced as pets that have subsequently escaped. Whether these escapees have established breeding populations and, if so, their impact is not known.

Scuds (Amphipoda) are found in all types of permanent standing and slow flowing water. They are slightly flattened laterally. Some may reach over a cm long. Three species have be reported from SK. Gammarus lacustris Sars, has no spines along the back and a tiny "flagellum" on the first antennae. They are usually larger than Hyallela azteca (Saussure), which has spines on its back and no "flagellum". Diporeia hoyi (= Ponoporeia affinis) (Bousfield) is found only in deep, cold lakes. In this species the first antennal segment is longer than the second. Males have extremely long antennae compared to the females.

Gammarus lacustris Hyallela azteca

Tadpole shrimp (Nonostraca) are relatively uncommon in Saskatchewan. They inhabit temporary ponds. They can reach 2 to 3 cm long in some habitats. Three species belonging to two genera occur in SK Triops longicaudatus LeConte, Lepidurus lynchi Linder and L. couesii Packard.

Opossum Shrimp (Mysidacea) are found in some cold, deep lakes of northern Saskatchewan. Only one species has been recorded in the province, Mysis relicta (Loven).

Fairy shrimp (Anostraca) are usually associated with temporary ponds where they can become numerous in mid-spring. They are usually less than 2 cm long. In the picture the female is at the top. You can see the egg sacs. The male is at the bottom with claspers.

Seed shrimps (Ostracoda) are common in ponds and lakes. They resemble swimming seeds a couple of mm long. Closer inspection will reveal a clam-like shell.

Clam shrimp (Conchostraca) can be common in shallow ponds and lakes. They first appear to be like small swimming clams. Length is about 1.5 cm or less.

Waterfleas (Cladocera) can become so abundant in ponds and shallow water that they form reddish clouds in the water. They swim with a jerky motion using their antennae. They rarely get larger than a couple of mm.


Springtails (Collembola) Mature insects are tiny (1-2 mm long). Most have a forked abdominal appendage or which acts as a spring. This group is found in wet soils and on the water surface of all types of aquatic habitats. They prefer calmer conditions so they do not get trapped in the surface film. They can be seen hopping like fleas on the water. Often on warm spring days they can be seen on the snow surface. Hence their other common name "snowfleas".

Mayflies (Order: Ephemeroptera) The immature stages (larvae) all have gills along the body (abdomen). They will also have one or two filaments at the end of the abdomen. The body form can be very flattened in some groups, especially in fast flowing water, to streamlined, almost minnow-like, in other groups. Still other larvae have their bodies adapted for burrowing into the mud substrates of lakes and rivers. Adults have two large forewings and two tails. If the wings of the adult are cloudy it usually indicates the specimen is a subadult.

mayfly larva mayfly larva

Stoneflies (Order: Plecoptera) larvae have some what flattened bodies, two segmented caudal tails and, in many, tufts of gills at the base of each leg and sometimes on the first two or three abdominal segments. Size can range from 5 mm to over 5 cm. The adults hold their two pairs of wings flat over their body and the caudal filaments are very much reduced. Stoneflies are usually associated with cold, clean flowing water.

Dragonflies and Damselflies (Order: Odonata) adults have four wings and an elongated abdomen. The wings can be held outwards from the body or along the body depending on the group. Larvae have hinged mouthparts. The damselflies have three leaf like "gills" at the end of the body

True Bugs (Hemiptera) It is relatively easy to identify the major families, and some species, of aquatic true bugs found in Saskatchewan. True bugs have in common a leathery fore wing and mouthparts shaped into a sucking beak. Water striders are common in quiet areas of rivers, lakes and ponds where they can be seen walking on the water surface. Water boatman are common in most water types. They range in size from 3 mm to about one cm. Backswimmers are usually not as common but by no means rare. They are about one cm long and have a distinctive keeled back and swim upside down. The single species of giant water bug found in Saskatchewan can be 8 cm long making it our largest aquatic insect.

giant water bug water boatman backswimmer water strider

Caddisflies (Trichoptera) Adult caddisflies look like moths but lack the coiled mouthparts that moths and butterflies have. The adult wings are covered by hairs. The wings are held tightly over the abdomen when the insect is at rest. The larvae have a well-developed head, three pairs of legs and a soft segmented body. Many caddisfly groups build cases, "houses", out of sand grains or pieces of plant material that they drag around with them. Other larvae construct stationary houses.

Aquatic Moths (Lepidoptera) look like other moths in the adult stage. As larvae they live in water usually associated with plants. Some create small "houses" out of plant material. And some have bodies covered in gills.

Spongilla flies (Neuroptera) are associated with freshwater sponges, which the larvae feed on. The larvae are only a couple of mm long at most and have needle like mouthparts to suck the contents out of sponge cells. The adults have four wings and are also small.

Alderflies (Megaloptera) usually are not very common. The larvae look like some beetle larvae with gills along the sides of the body and a terminal filament at the end of the body. The adults are dark and have very thick wing veins on their four wings.

Wasps (Hymenoptera) are parasitic on other aquatic insects. They are usually only seen as adults. Since most look like tiny terrestrial wasps they have to be collected in traps in the water to ensure they are aquatic.

Beetles (Coleoptera) come in variety of shapes as larvae but as adults all have the forewings hardened into coverings called elytra.

True flies (Diptera) adults all have only one pair of wings. The back wings are modified into balancing structures called "halteres". All the biting flies such as mosquitoes, blackflies, horseflies, deerflies and no-see-ums belong to this group. The larvae have no true jointed legs and are tube-shaped with many different body types based on this design.

blackflies phantom midge larva bloodworms mosquito false crane fly larva blackfly larva & pupa mosquito crane fly larva