Insect Orders
Insect Identification: The Basics
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What is an Insect
The Abdomen
The abdomen is composed of 11 segments. However, some of the segments may be fused, and upon examination fewer legs may be visible.
On mayfly nymphs, gills can be seen on the dorsal side. These are extensions of the the tracheal system. The last segment bears appendages that are useful in identifying some kinds of insects, including the cerci (Figure a.), paraprocts (Figure b.), and epiproct (Figure c.). Also included on the last segment are the anus and reproduction structures. Some insects also have filiments that extend off of the tip of the abdomen (Figure d.)
On some insect larvae, prolegs (Figure e.) are present on the last segment (e.g. caterpillars). Prolegs are not true legs in the sense that they are not segmented. However, they aid the insect in moving.
Tools and Methods for Collecting Aquatic Insects