Insects (Insecta) are the most diverse of all animal groups. There are more species of insects than there are all other species combined. Their numbers are nothing short of remarkable, both in terms of the numbers of individuals as well as the number of species. In fact, there are so many insects that no one knows quite how to count them all. The best that can be done is to make estimates.
Scientists approximate that there may be as many as 30 million species of insects alive today. To date, over one million have been identified. At any one time, the number of individual insects alive on our planet is stagering—some scientists estimate that for ever human alive today there are 200 million insects.
Insects belong to the Subphylum Hexapoda, a group commonly referred to as hexapods and whose members have six legs.
Some basic characteristics of insects include:
- three main body parts - the body of an insect consists of three basic parts—a head, a thorax and an abdomen
- small body size -
- three pairs of legs - insects have three pairs of legs that are located on their thorax
- two pairs of wings - insects have two pairs of wings that are located on their thorax
- metamorphosis - many insects undergo a transition through several stages in their development
- compound eyes - insects have a pair of compound eyes
- complex mouthparts - insects generally have complex mouthparts that are often specialized according to the feeding habits particular to a species
- a pair of antennae - insects have a pair of antennae located on their head
Classification
- Kingdom: Animalia
- Phylum: Arthropoda
- Class: Insecta
The Class Insecta contains the following subgroups:- Order: Archaeognatha (bristletails)
- Order: Thysanura (silverfish)
- Order: Ephemeroptera (mayflies)
- Order: Odonata (damselflies and dragonflies)
- Order: Orthoptera (crickets and grasshoppers)
- Order: Plecoptera (stoneflies)
- Order: Grylloblattodea (rock crawlers)
- Order: Phasmotodea (stick and leaf insects)
- Order: Dermaptera (earwigs)
- Order: Mantodea (mantids)
- Order: Blattodea (cockroaches)
- Order: Isoptera (termites)
- Order: Embioptera (web-spinners)
- Order: Zoraptera (angel insects)
- Order: Psocoptera (barklice and booklice)
- Order: Phthiraptera (parasitic lice)
- Order: Hemiptera (bugs)
- Order: Thysanoptera (thrips)
- Order: Megaloptera (dobsonflies and alderflies)
- Order: Rapdhidioptera (snakeflies)
- Order: Neuroptera (antlions and lacewings)
- Order: Coleoptera (beetles)
- Order: Strepsiptera (strepsipterans)
- Order: Mecoptera (scorpionflies)
- Order: Siphonaptera (fleas)
- Order: Diptera (flies)
- Order: Trichoptera (caddisflies)
- Order: Lepidoptera (moths and butterflies)
- Order: Hymenoptera (bees, wasps, ants, sawflies)
Range and Habitat:
The success of insects as a group is reflected by the diversity of habitats they live in. Insects are most numerous in terrestrial environments such as deserts, forests, and grasslands. They are likewise numerous in freshwater habitats such as ponds, lakes, streams, wetlands. Insects are relatively scarce in marine environments but are more common in brackish waters such as salt marshes and mangroves.
Refs:
- Burnie D, Wilson DE. 2001. Animal. London: Dorling Kindersley. 624 p.
- Myers, P. 2001. Class Insecta, Animal Diversity Web. September 20, 2005
