Immature Insects Rick Story, Department of Entomology

Types of Insect Development 1)Incomplete (egg nymph or larva adult) 2)Complete (egg larva pupa adult)

Insect Growth - external skeleton -grows with successive molts -each stage is an instar -typically 5-7 instars for larval growth

Insect Metamorphosis - change in body form from immature to adult stage

Incomplete Metamorphosis Immatures look like adults except: 1)Smaller 2)Lack wings 3)Lack genitalia

Incomplete Metamorphosis Immatures look like adults: 1)Same mouthparts 2)Feed on same plants 3)Occur together with adults 4)Have compound eyes

Complete Metamorphosis -immatures do not look like adults -have an inactive pupal stage for transformation

Complete Metamorphosis Immatures unlike adults: 1)Different mouthparts 2)Different host plants 3)Do not typically occur together 4)Lack compound eyes

Identification of Immatures Incomplete development orders – characters similar for nymphs and adults Complete development orders- characters completely different

Main orders with complete development Neuroptera : green + brown lacewings Lepidoptera : caterpillars (moths) Hymenoptera : sawfly larvae, ants, bees, wasps Diptera : maggots (flies) Coleoptera : white grubs, weevils, wireworms (beetles)

Neuroptera - Larvae are predators, with well developed legs and an elongated body -sickle shaped mandibles with blood groove diagnostic character

Lepidoptera - Larvae (caterpillars) are plant feeding and have chewing mouthparts -caterpillar body form diagnostic (cylindrical body, thoracic legs well developed, abdominal prolegs present)

Diptera - Larvae with variable feeding habits and chewing mouthparts -body with head capsule partially to completely reduced, no thoracic legs, soft bodied, white, often occur in damp habitats.

Coleoptera - Larvae with chewing mouthparts, plant feeding or predators -Have well developed head capsule, thoracic legs present (usually), and lack abdominal legs

Hymenoptera - sawflies: caterpillar body form (prolegs lack hooks), feed on foliage -bees, wasps, ants: grub-like body form with well developed head capsule and no thoracic legs.

Author: Rick Story