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 – characterssimilar for nymphs and adults

Complete development orders- characterscompletely 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

rstory@agcenter.lsu.edu