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General information

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.


Insects of Ontario

Ontario is a huge province with the widest range of environments of any Canadian province - from a narrow strip of tundra on the shores of Hudson Bay, to the mixed forests west of Lake Superior, the coniferous forests of the Canadian Shield, the eastern deciduous forests of Southern Ontario and the Carolinian woodlands in the extreme south.

Insects are found in all these environments though species diversity (not necessarily numbers) tends to decrease as you go north.

Some major groups of insects include:

Dragonflies and damselflies - Order Odonata - These insects are good indicators of healthy freshwater habitats as they will disappear when water becomes polluted. Adults eat mosquitoes and other insects.

Mayflies - order Ephemeroptera - These are small insects that spend most of their lives in the water. Adults emerge in great numbers but live only for a day. Mayflies are an important food source for many fish.

Grasshoppers, mantises and crickets - order Orthoptera. Many insects of this order produce sounds by rubbing body parts together.  

Bugs - order Hemiptera, suborder Homoptera - These are the true bugs; their lower lip is modified into a sucking tube that the insect inserts into plant or animal tissues in order to feed. Aphids and plant hoppers are bugs.

Butterflies and moths - order Lepidoptera - These are the familiar beautiful insects that we readily welcome to our gardens. Besides being beautiful to look at, they are important pollinators.

Beetles - order Coleoptera - This order includes the familiar June beetle, ladybird beetle and fireflies. Beetles are also pollinators but play an extremely important role in the recycling of animal dung and dead animals.

Flies - order Diptera - True flies have a single pair of wings; their hind wings are reduced to stalked knobs called halteres that they use to keep their stability while flying. Flies are important pollinators and also feed on dead carcasses so that nutrients are recycled back into the environment. 

Ants, wasps and bees - order Hymenoptera - We are all familiar with these insects and often consider them to be a nuisance. However, they are important pollinators of many of our agricultural plants including apples, tomatoes, beans, peas, oilseed and fibre crops.