Lecture 7: Intro to Metamorphosis and Taxonomy

Metamorphosis

the process of changing from an immature to an adult

Ametabolous

• “No metamorphosis”

• Primitive and wingless taxa

• Immature resembles adult except for size and sexual maturity

• Term for immature: Nymph

Paurometabolous

• gradual metamorphosis

• immature similar to adult except size, sexual maturity, and wings

• nymphs and adults share the same habitat

• wings progressively develop externally (wing pads present in nymphs)

Hemimetabolous

• half metamorphosis

• immature and adults have different habitats

• naiads aquatic, adults terrestrial

• Term for immature: Naiad

• wings progressively develop externally (wing pads present on naiads)

Holometabolous

• complete metamorphosis

• immature and adult occupy different habitats

• term for immature: Larvae

• pupal stage present

• wings develop internally during pupal stage

Pupal stage

• major internal reconstruction

• does not feed

• usually inactive

• sometimes covered in a protective case

• pupa cuticle provides a “mold” for adult form

Exarate pupae

• appendages free

• often look like pale, mummified adults

• most beetles, wasps, and honey bees

Coarctate pupae

• similar to exarate but pupa is contained in the exuviae of the last instar (puparium)

• house flies, blow flies

Obtect pupae

• Appendages fused to the body

• May be covered in a silken cocoon before molting to pupa (generally moths)

• May suspend by a silken line

Class Entognatha

• The insect like hexapods

• Primitively wingless, soft-bodied, no metamorphosis

Entognathous

mouthparts are withdrawn into head and emerge to feed

Order collembola

• not insects

• the springtails

• refers to collophone on 1st abdominal segment

• has a spring (furcula) that allows them to jump

Class Insecta

• 3 body segments

• 3 pair of legs

• 2 pair of wings (some lost)

• 1 pair of antennae

Insects are ectonathous

true, their mouthparts are external

spring tails are entognathous

true

Apterygota

• the primitive insects (first)

• Ancestrally wingless

• ametabolous

• long antennae, long, cerci, and medial caudal filament

Order Microcoryphia

• jumping bristletails

• small head with contiguous eyes

• humped thorax

• maxillary palps long and leg like

Order Zygentoma

• silverfish and firebrats

• dorsoventrally flattened

• silvery scales

• fast moving ( do not jump )

• scavengers

• In dark areas

silverfish

• cool, humid places

• bathrooms, basements, flood damaged areas

firebrats

• warm humid places

• pipe insulation, boiler rooms, bakeries