Insects and Their Relatives Section 30.3

Insect diversity The largest group of animals Four important orders:  Coleoptera – ‘shield-winged’ like beetles  Diptera – ‘two-winged’ like flies  Lepidoptera – ‘scale-winged’ like butterflies  Hymenoptera – ‘membrane-winged’ like wasps

Coleoptera

Green bottle fly

Butterflies

Ants

Insect Body Plan 1. Head – has mandibles, specialized mouthparts, one pair of antennae and usually 1 pair of compound eyes 2. Thorax – has three pairs of jointed walking legs; some without wings, others with 1 or 2 pairs of wings 3. Abdomen – has 9 – 11 segments

Insect body parts

Insect Life Cycle Complete metamorphosis: Almost all insect species egg  larva  pupa in chrysalis  adult Incomplete metamorphosis: egg  nymph  (several molts)  adult

Insect Life Styles Flight: Insects were the first animals to develop flight Wings develop from sacs of the body wall of the thorax Most insects can fold their wings over the abdomen – some cannot Social insects: Ants, bees, wasps, and termites Division of labor within the colony

Many insects can fly

Ants are social insects

Insect relatives Centipedes –1 pair of legs per segment; carnivores Millipedes – 2 pair of legs per segment; herbivores

Centipedes – 1 pair of legs/segment

Millipedes – 2 pairs of legs/segment