Insect Metamorphosis, Molting, and Cuticle - Video Notes

A comprehensive set of vocabulary flashcards covering metamorphosis, molting, cuticle structure, embryology, larval forms, pupal types, hormonal control, growth patterns, and environmental effects.

Metamorphosis

Developmental process in insects involving dramatic body changes; two main patterns are hemimetabolous (egg–nymph–adult) and holometabolous (egg–larva–pupa–adult).

Hemimetabolous

Partial metamorphosis with life stages: egg, nymph, and adult; nymphs resemble adults.

Holometabolous

Complete metamorphosis with life stages: egg, larva, pupa, and adult; larva and adult look very different.

Egg

The fertilized egg stage that hatches into immature forms (larva or nymph) depending on species.

Larva

Immature, typically worm-like stage; in holometabolous insects, stage between egg and pupa.

Nymph

Immature stage in hemimetabolous insects that resembles the adult but is often smaller and not fully winged.

Instar

Growth stage between two successive molts; often refers to larval stages.

Stadium

Time interval between successive molts (ecdyses) for all life stages.

Molting

Process of shedding the old cuticle and forming a new one to grow.

Apolysis

Separation of the old cuticle from epidermal cells before molt.

Ecdysis

Shedding of the old cuticle during molt.

Molting fluid

Enzymatic fluid secreted during apolysis that digests old endocuticle and provides materials for new cuticle.

Endocuticle

Soft inner cuticle layer with little sclerotization.

Exocuticle

Rigid, sclerotized outer cuticle that provides structural support.

Epicuticle

Outer, water-loss–preventing layer; coated with wax/cement and may have six sublayers.

Pore canal

Tiny canals that transport wax and cement to outer cuticle layers; do not reach the surface.

Epidermis

Single layer of cells beneath the cuticle that secretes new cuticle.

Intermolt stage

Period between molts in the insect’s life cycle.

Polypod

Larval form with cylindrical body, short thoracic legs, and abdominal prolegs.

Oligopod

Larva lacking abdominal prolegs but with functional thoracic legs.

Apod

Maggot-like larva lacking true legs.

Decticous

Pupal mandibles that are articulated (move at joints).

Adecticous

Pupal mandibles that are non-articulated.

Exarate

Pupal type where appendages are not pressed tightly against the body.

Obtect

Pupal type where appendages are cemented to the body and the cuticle is heavily sclerotized.

Zygote

Fertilized egg; the initial cell that begins development.

Eclosion

Emergence from the egg (hatching event).

Oviposition

Laying of eggs by the female.

Germ band

Embryonic structure that forms the segmented body plan.

Procephalon

Anterior embryonic region that develops into the head.

Mandible

Jaw-like mouthpart used for chewing.

Labrum

Upper lip structure of the insect's mouthparts.

Spiracle

External respiratory opening on the abdomen or thorax.

Antenna

Sensory appendage on the head.

Egg tooth

Projection used by hatchlings to break the eggshell.

PTTH

Prothoracicotropic hormone; brain neuropeptide that stimulates molting and metamorphosis.

Ecdysone

Steroid hormone from the prothoracic gland that triggers molting; converted to 20-hydroxyecdysone.

20-hydroxyecdysone

Active molting hormone that drives the molt process.

Juvenile Hormone (JH)

Hormone from the corpora allata that modulates molts and development; high levels promote larval molts, low levels permit larval-pupal molts; absent at pupal-adult molt.

Corpora allata

Glands that secrete Juvenile Hormone.

Indeterminate growth

Molting can continue throughout an arthropod’s life; no fixed number of molts.

Determinate growth

Set number of molts before adulthood (e.g., stink bugs 4; crickets 8).

Univoltine

One generation per year.

Bivoltine

Two generations per year.

Multivoltine

More than two generations per year.

Diapause

Arrested development with adaptive physiological changes; resumes after stimuli, not necessarily with return of suitable conditions.

Obligatory diapause

Diapause that is non-optional; must occur under certain conditions.

Facultative diapause

Diapause that is optional and can be triggered by environmental cues.

Quiescence

Halted or slowed development due to unfavorable conditions, resuming when conditions improve.