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Toronto Entomologists’ Association
Toronto, Ontario Canada |
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Insects belong to the group Arthropoda that
includes spiders, crustaceans and millipedes. Insects (Class Insecta)
are characterized by the following: they have a head that contains the
eyes, antennae and mouthparts, a thorax to which the legs and wings attach
and an abdomen that contains the organs and usually has no appendages
except at the tip, where egg-laying tubes, claspers or other appendages
are found. Insects have a hard exoskeleton to which its muscles attach. They have a heart and 'blood', called hemolymph that circulates through the body transporting nutrients and hormones (but not oxygen) and regulating temperature. Insects breathe through a system of air tubes (trachea) that open at holes, called spiracles, on the surface of the insects' body. Insect wings are unique, new structures, not modified legs as the wings of birds and bats are. Life cycle of insects Most insects have only one generation per year but some have more and some require more than one year to complete a cycle. In their development, they go through a change, called metamorphosis. Some insects, including dragonflies, grasshoppers and bugs, undergo simple metamorphosis: adults lay eggs which hatch into a larval or nymphal stage from which the adult develops. Others, such as butterflies, beetles and ants, undergo complete metamorphosis: adults lay eggs which hatch into larvae, which then change into a pupal resting stage from which the adult eventually emerges.In Ontario, insects need to survive in some form over the winter, and in fact, may require colder temperatures for proper maturation. Insects may overwinter as an egg, larva, pupa or an adult. Most adult insects live for a few days to a few weeks. |