Insect Characteristics Rainier Jr/Sr High School Advanced Life Science Mr. Taylor

Insect Characteristics 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.

Insect Characteristics 4 main orders of Insects (several minor orders will be ignored) Diptera: “two-winged” includes flies and mosquitoes Lepidoptera: “scale-winged” includes butterflies and moths Hymenoptera: “membrane-winged”: includes bees, wasps, and ants. Many social insects. Coleoptera: “shield-winged”: beetles. Largest group of insects.

Insect Characteristics Body plan: 3 divisions Head 1st segment have 2 antennae … sensory 2nd segment has mandibles … obtain food Next segments have other specialized mouthparts. Insects are extremely specialized in their methods of obtaining food supplies. Also have compound eyes.

Insect Characteristics Body plan: 3 divisions Thorax 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.

Insect Characteristics Body plan: 3 divisions Abdomen 9-11 segments Contain most of digestive and reproductive organs. No appendages attached to abdomen.

Insect Characteristics Digestive system Specialized mouthparts for specialized feeding allow for minimal competition.

Insect Characteristics Digestive system Food passes through Mouth; food is ground up Crop: 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.

Insect Characteristics Excretory system: Malpighian tubules: eliminate nitrogen wastes as urea: allows for conservation of water.

Insect Characteristics Respiratory System Most have spiracles and tracheae.

Insect Characteristics Nervous System Ventral 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 Characteristics Life Cycle Most undergo complete metamorphosis Adult lays egg Egg hatches to larva Larva wraps in chrysalis to become pupa Pupa emerges as an adult Most larva feed on different food than adults: a means of minimizing competition.

Insect Characteristics Life Cycle Some undergo incomplete metamorphosis Adult lays egg Egg hatches into a wingless nymph. Less mature nymph molts to more mature nymph. Several nymphs later, the adult form appears.

Insect Characteristics Reproduction Sexual Internal and external fertilization Some females have pouches to store sperm, often for long periods of time Eggs often resistant to heat, cold, dryness. This allows survival of species during long periods of unfavorable conditions (winter, drought, etc)

Insect Characteristics Flight First 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.