Insects in the Big Picture
Basic Insect Morphology
The insect body is divided into three parts:
- the head carries
- one pair of antennae (crustaceans have two) which commonly support the
sense of touch and something like 'smell'
- two compound eyes and, in most cases, one or more simple eyes
- three pairs of mouth parts, usually including mandibles and/or a siphon formed from one pair of the appendages
- a rudimentary brain
- the thorax bears
- all three pairs of legs, which often include sensory organs for taste and/or touch
- zero, one, or two pairs of wings. Most insects have two pairs of wings
(in the beetles the second pair is hardened to form a protective cover for the
flying wings), but the Order Diptera has only one. Most orders include some wingless species or
species with some members which are wingless (eg. the males of many ants in the order Hymenoptera.
The larvae (grubs, maggots, caterpillars, etc.) of the completely
metamorphosing insects do not have wings and the nymphs (terrestrial) and
naiads (aquatic) of the incompletely metamorphosing insects have wing buds.
Wings only appear in the final molt of the nymph or naiad to the adult form of the species.
- the abdomen holds
- the breathing apparatus
- digestive system
- reproductive organs and, in the females of many species, an ovipositor for
depositing eggs (eg. a wasp's sting)
- miscellaneous items (eg. poison glands and sacs in bees, noise-making air
sacs in cicadas)
In addition to these features, most insects have hairs which are sensitive to
such things as the movement of air, humidity, and temperature, as well as to
Insects in the Big Picture...3, March 1996