insect characteristics

Insect Characteristics

Rainier Jr/Sr High SchoolAdvanced Life Science

Mr. Taylor


Insects are the largest single class of organisms with >700,000 named species

This is > ½ of the total named species of organisms (including plants and fungi!)

Insects are the only invertebrates to fly … resulting in a great natural selective advantage.


4 main orders of Insects (several minor orders will be ignored)Diptera: “two-winged” includes flies and

mosquitoesLepidoptera: “scale-winged” includes butterflies

and mothsHymenoptera: “membrane-winged”: includes

bees, wasps, and ants. Many social insects.Coleoptera: “shield-winged”: beetles. Largest

group of insects.


Body plan: 3 divisionsHead

1st segment have 2 antennae … sensory2nd segment has mandibles … obtain foodNext segments have other specialized mouthparts.

Insects are extremely specialized in their methods of obtaining food supplies.

Also have compound eyes.


Body plan: 3 divisionsThorax

3 fused segments each have a set of walking legs.2 of the segments also have wings on most insects.Wings are made of chitin with supporting veins.

Veins are filled with air, not blood or other fluid.


Body plan: 3 divisionsAbdomen

9-11 segmentsContain most of digestive and reproductive organs.No appendages attached to abdomen.


Digestive systemSpecialized mouthparts for specialized feeding

allow for minimal competition.


Digestive systemFood passes through

Mouth; food is ground upCrop: more grinding, addition of digestive enzymes.Gizzard; mixing of food, enzymes act on food.Midgut/stomach; most absorption here.Anus; indigestible wastes are passed out.


Excretory system:Malpighian tubules: eliminate nitrogen wastes

as urea: allows for conservation of water.


Respiratory SystemMost have spiracles and tracheae.


Nervous SystemVentral nerve cords with ganglia in each

segment.Brain in anterior segment.Also have antennae (1 pair): chemo- and touch-

receptors. Sensors are extremely sensitive.

Insect CharacteristicsLife Cycle

Most undergo complete metamorphosisAdult lays eggEgg hatches to larvaLarva wraps in chrysalis to become

pupaPupa emerges as an adult

Most larva feed on different food than adults: a means of minimizing competition.


Life CycleSome undergo incomplete metamorphosis

Adult lays eggEgg hatches into a wingless nymph.Less mature nymph molts to more mature nymph.Several nymphs later, the adult form appears.


ReproductionSexualInternal and external fertilizationSome females have pouches to store sperm,

often for long periods of timeEggs often resistant to heat, cold, dryness.

This allows survival of species during long periods of unfavorable conditions (winter, drought, etc)


FlightFirst animals with wings to appear in fossil

record.This allowed insects to invade and exploit new

environments.This allowed insects to escape predators better

Most have 2 sets of wings, some have only 1 (house flies), a few have no wings (fleas).

Usually only one set of wings used for flight.

insect characteristics

Documents