Insects - All Around Us!

There is a famous cartoon that shows a bunch of insects having a very human-like cocktail party; one beetle-like creature, holding a highball in his anthropomorphic hand, lists the great diversity of orders, families and species in the insect class but concludes "I can't shake the feeling that we're all just a bunch of bugs!"

With around one million named species and perhaps several times that number unnamed in existence, insects account for a great majority of the species of animals on earth. They are a tremendously successful group. Insects can be found in almost all terrestrial and freshwater habitats, from the driest deserts to freshwater ponds, from the canopy of a tropical rainforest (where their diversity is unbelievably great) to the arctic wastes. A few species are even marine. Their feeding habits are similarly varied; almost any substance that has any nutritive value is eaten by some group of insects.

Insects also show huge variety in shape and form. Almost the only condition their group does not attain is very large body size. A number of features, however, are shared by most kinds of living insects. In addition to the general characteristics of uniramians (see below), these include a body composed of three tagmata: a head, thorax, and abodmen; a pair of relatively large compound eyes and usually three ocelli located on the head; a pair of antennae, also on the head; mouthparts consisting of a labrum, a pair of mandibles, a pair of maxillae, a labium, and a tonguelike hypopharynx; two pairs of wings, derived from outgrowths of the body wall (unlike any vertebrate wings); and three pairs of walking legs.

Insects have a complete and complex digestive tract. Their mouthparts are especially variable, often complexly related to their feeding habits. Insects "breathe" through a tracheal system, with external openings called spiracles and increasingly finely branched tubules that carry gases right to the metabolizing tissues. Aquatic forms may exchange gases through the body wall or they may have various kinds of gills. Excretion of nitrogenous waste takes place through Malpighian tubules. The nervous system of insects is complex, including a number of ganglia and a ventral, double nerve cord. The ganglia are largely independent in their functioning; for example, an isolated thorax is capable of walking. Yet ganglia also use sensory output. A grasshopper with one wing removed can correct for this loss and maintain flight, using sensory input from its brain. Sense organs are complex and acute. In addition to ocelli and compound eyes, some insects are quite sensitive to sounds, and their chemoreceptive abilities are astounding.

In scientific taxonomy, insects are classified in the following order:

Kingdom: Animalia

Phylum: Arthropoda

Subphylum: Uniramia

Class: Insecta

Order: Microcoryphia
Order: Thysanura (silverfish)
Order: Paleoptera
Order: Ephemeroptera (mayflies)
Order: Odonata (dragonflies)
Order: Neoptera
Order: "Orthopteroids"
Order: Grylloblattaria
Order: Phasmida (stick and leaf insects)
Order: Orthoptera (grasshoppers, crickets, katydids)
Order: Mantodea (mantises)
Order: Blattaria (cockroaches)
Order: Isoptera (termites)
Order: Dermaptera (earwigs)
Order: Embiidina
Order: Plecoptera (stone flies)
Order: "Hemipteroids"
Order: Zoraptera
Order: Psocoptera (book and bark lice)
Order: Phthiraptera
Order: Heteroptera (true bugs)
Order: Homoptera (cicadas, aphids, scale insects)
Order: Thysanoptera (thrips)
Order: Holometabola
Order: Neuroptera (lacewings, ant lions, dobsonflies, etc.)
Order: Coleoptera (beetles)
Order: Strepsiptera
Order: Mecoptera (scorpion flies)
Order: Siphonaptera (fleas)
Order: Diptera (flies)
Order: Trichoptera (caddisflies)
Order: Lepidoptera (moths and butterflies)
Order: Hymenoptera (ants, bees, wasps - there are 60-70 families in this order!)

Suborder: Apocrita

Family: Formicidae (ants)

Genus: Atta

Species: Atta texana (common Texas black ant)