Updates from March 10, 2004

Instar: Many invertebrates molt through dozens of progressively larger and better-developed stages as they grow. Each of these stages is known as an instar. Hard-bodied nymphs typically molt through more instars than soft-bodied larvae.

Lateral: To the side.

Nymph: The juvenile, underwater stages of mayflies, stoneflies, dragonflies, and damselflies and other aquatic insects whose juvenile stages are covered by hard exoskeletons. The word can also refer to the fishing flies which imitate these creatures, in which case it is used as a blanket term for flies imitating any underwater stage of an invertebrate (except for crayfish and leeches).

Posterior: Toward the back of an organism's body. The phrase "posterior to" means "in back of."

Tibiae: A middle segments in the leg of an insect, located between the femur and the tarsus.

Truncate: Cut off. This is often used to describe the square appearance of the gills of Maccaffertium mayfly nymphs, for example, as opposed to the pointed gills of the closely related genus Stenacron.

Tubercles: Various peculiar little bumps or projections on an insect. Their character is important for the identification of many kinds of insects, such as the nymphs of Ephemerellidae mayflies.