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Macroinvertebrates home			Streams project

Identifying orders of aquatic macroinvertebrates

Latin names for the orders link to the Tree of Life.  Characteristics listed are for the immature life cycle stages typically found in aquatic habitats.

Ephemeroptera : Mayflies

- 3 (or less commonly 2) "tails" (cerci)

- 1 claw per foot

Plecoptera : Stoneflies

- 2 "tails" (cerci)

- 2 claws per foot

Trichoptera : Caddisflies

- 3 pairs of jointed legs

- 1 pair of anal claws

- Frequently in cases

Diptera : True Flies

- jointed legs absent

- but there may be 'prolegs'

Coleoptera : Beetles

-There are no obvious characteristics to simplify identification of this group so we have provided the following pictures of the common beetles we find (click to enlarge):

Odonata: Dragonflies and damselflies

-Members of both suborders have hinged labial masks underlying their heads.

-Anisoptera: Dragonflies are distinctly robust with bodies typically as wide or wider than their heads

-Zygoptera: Damselfly bodies are slimmer than their head width and have three leaf-like gills on their tail end.  The gills sometimes break off, but the stumps are usually visible under a microscope.

Megaloptera: Dobsonflies, alderflies, and fishflies are predatory insects with paired lateral filaments on each abdominal segment.

Dobsonflies have 2 pairs of anal claws and were the most common megalopterans in our samples.

This image from wikimedia commons

Anal claws are lacking in the alderflies; a single prominent caudal filament or 'tail' distinguishes the alderflies from most other macroinvertebrates:

Non-insects:  A number of non-insect macroinvertebrates are common in our samples.

Isopoda: Isopods have 7 pairs of walking legs and are  flattened top to bottom (dorsoventrally).

Amphipoda: Closely related to the isopods, the amphipods are flattened side to side.

Collembola: Springtails are non-insect hexapods.  They have a distinctive ventral tube on the first abdominal segment.  Because the rear legs tend to sweep back, the tube frequently appears between the last pair of legs.  A forked spring mechanism (forcula) typically points back in preserved specimens, but sometimes remains held under the body.  Click on the thumbnail image for a close look.