Insects: Diversity, Classification, and Key Concepts (Lecture Notes)

A vocabulary set of key insect terms drawn from the lecture notes, focusing on classification, anatomy, metamorphosis, behavior, ecological roles, and practical concepts like pheromones and biocontrol.

Insect

A six‑legged, three‑part arthropod (head, thorax, abdomen) with an often‑exoskeleton of chitin and typical wings and antennae.

Arthropoda

Phylum of invertebrates with segmented bodies, jointed limbs, and an exoskeleton.

Chitin

A tough polysaccharide forming the insect exoskeleton; provides structural support and protection.

Hexapoda

Subphylum including six‑legged arthropods; comprises the class Insecta and is defined by three pairs of legs.

Elytra

Hardened forewings of beetles that protect the hind wings and abdomen.

Exoskeleton

Rigid external skeleton made of chitin that supports and protects the body.

Entognatha

Class of wingless, ametabolous arthropods with mouthparts retracted inside the head; grouped with insects in Hexapoda; includes Protura, Diplura, Collembola.

Protura

Order within Entognatha; small, wingless, primitive insects with internal mouthparts.

Diplura

Order within Entognatha; two‑pronged bristletails; wingless and primitive.

Collembola

Order within Entognatha; springtails with mouthparts inside the head and a furcula for jumping.

Archaeognatha

Order within Apterygota; bristletails; humpbacked and wingless; good jumpers.

Thysanura

(Zygentoma) Silverfish and firebrats; flat, fast‑moving, long cerci.

Ephemeroptera

Mayflies; short adult life; aquatic naiads; subimago and imago stages.

Odonata

Dragonflies and damselflies; large eyes; long bodies; aquatic nymphs.

Plecoptera

Stoneflies; aquatic nymphs; indicators of water quality.

Dermaptera

Earwigs; pincers on abdomen; chewing mouthparts.

Dictyoptera

Group including cockroaches and mantids; in some classifications includes Blattodea and Mantodea.

Blattodea

Cockroaches; elongated bodies; ootheca; chewing mouthparts and running legs.

Isoptera

Termites; social insects; cellulose digestion.

Mantodea

Praying mantises; predatory front legs; camouflage.

Embioptera

Webspinners; spin silk from front legs.

Grylloblattodea

Ice crawlers/rock crawlers; cold‑dwelling, wingless insects.

Mantophasmatodea

Heelwalkers; resemble mantids and stick insects; large arolia and distinctive walking behavior.

Orthoptera

Grasshoppers, crickets, and katydids; jumping hind legs; chewing mouthparts.

Phasmatodea

Stick and leaf insects; camouflage; long bodies.

Zoraptera

Angel insects; rare, termite‑like.

Hemiptera

True bugs; piercing‑sucking mouthparts; wings often membranous or leathery; X‑pattern on the back.

Homoptera

Suborder with uniform wing texture; includes cicadas, aphids, whiteflies, scale insects.

Cicadidae

Cicadas; nymphs underground; loud songs.

Cicadellidae

Leafhoppers; large family; important plant disease vectors.

Fulgoridae

Planthoppers; cryptically shaped and colored; diverse forms.

Psyllidae

Psyllids or jumping plant lice; small insects with beaks and waxy coverings.

Aleyrodidae

Whiteflies; wings and bodies often with wax; nymphs immobile on undersides of leaves.

Aphididae

Aphids; sap‑sucking pests and viral vectors; diverse and abundant.

Coccidae

Soft scale insects; sedentary; protective coverings; plant pests.

Miridae

Plant bugs; diverse; pests and some predators.

Lygaeidae

Seed bugs; mostly seed feeders; some predatory species.

Pentatomidae

Stink bugs; shield‑shaped; mostly herbivores with scent glands.

Reduviidae

Assassin bugs; predators; ambush or active hunters.

Nabidae

Damsel bugs; predatory.

Anthocoridae

Minute pirate bugs; predatory on pests.

Corixidae

Water boatmen; aquatic; surface‑dwelling scavengers or predators.

Gerridae

Water striders; skim the surface of water; elongated mid‑legs.

Nepidae

Water scorpions; aquatic ambush predators.

Belostomatidae

Giant water bugs; large predatory aquatic insects.

Notonectidae

Backswimmers; aquatic; swim on back with paddle-like legs.

Diptera

True flies; one pair of wings; halteres for balance; diverse feeding habits.

Nematocera

Diptera subgroup with multi‑segmented antennae (e.g., mosquitoes, crane flies).

Brachycera

Diptera subgroup with stylate antennae; often shorter antennae (e.g., robber flies).

Cyclorrhapha

Diptera subgroup with circular/pouched larval development; includes many families.

Syrphidae

Hoverflies; larvae eat aphids; adults feed on nectar.

Lepidoptera

Butterflies and moths; scale‑covered wings; complete metamorphosis.

Nymphalidae

Brush‑footed butterflies; large family; often bright patterned wings.

Papilionidae

Swallowtail butterflies; large and colorful; many species with osmeterium at larval stage.

Hesperiidae

Skippers; small to medium butterflies with hooked antennae; swift flight.

Pieridae

Whites and sulphurs; predominantly white or yellow with black markings; many migrate.

Lycaenidae

Blues, coppers, and hairstreaks; small; often iridescent; ant associations common.

Rhopalocera

Butterflies; traditional grouping of the true butterflies within Lepidoptera.

Heterocera

Moths; traditional grouping within Lepidoptera; typically nocturnal and with feathery or filiform antennae.

Osmeterium

Defensive organ in swallowtail larvae that everts to release a foul odor when threatened.

Repugnatorial glands

Defensive scent glands found in some insect larvae and adults (defense against predators).

Proboscis

Long mouthpart adapted for siphoning nectar in many Lepidoptera.

Spinneret

Median organ of silk glands in Lepidoptera; silk is spun through spinnerets during pupal or larval stages.

Holometabola

Insects with complete metamorphosis: egg, larva, pupa, and adult (e.g., Lepidoptera, Coleoptera, Diptera, Hymenoptera, etc.).

Hemimetabola

Insects with incomplete metamorphosis: nymphs resemble adults and molt into the adult form (e.g., Hemiptera, Orthoptera).

Pheromones

Chemical signals secreted by insects to communicate with same species, often for mating, trail marking, alarm, or aggregation.

Sex pheromones

Pheromones that attract mates over long distances.

Trail pheromones

Pheromones used by social insects to guide others to food or nest.

Alarm pheromones

Pheromones that warn colony members of danger.

Aggregation pheromones

Pheromones that attract individuals to gather at a site.

Trophallaxis

Direct transfer of food or fluids between individuals (mouth‑to‑mouth or anal‑to‑mouth), common in social insects.

Waggle dance

Honeybee dance that communicates the distance and direction to a food source using a figure‑eight pattern and the angle relative to the sun.

Eusociality

Social structure with cooperative care of offspring, reproductive division of labor, and overlapping generations.

Queen

Reproductive female in eusocial colonies (e.g., bees, ants, termites).

Drone

Male in bees/wasps whose role is to mate with the queen; often dies after mating.

Worker

Sterile or non‑reproductive female caste performing foraging, brood care, and nest maintenance.

Soldier

Defense caste found in some social insects like termites and some ants.

Bee hotel

Nest blocks or bundles providing nesting spaces for solitary bees and wasps; simulates hollow stems.

Biocontrol

Use of natural enemies (predators, parasitoids) to manage pest populations; includes classical, augmentative, and conservation strategies.

Dung beetle

Beetles that recycle dung by rolling, burying, and feeding on it; ecosystem engineers.

Myrmecochory

Seed dispersal by ants; seeds with elaiosome are taken to nests and germinate nearby.

Pantala flavescens

Wandering globe skimmer dragonfly; long‑distance transoceanic migrant.

Monarch migration

Long-distance, multi‑generational migration of Danaus plexippus; sun compass/navigation.

Mayfly subimago

Transitional winged stage between naiad and adult in Ephemeroptera; sexually immature.

Aposematic colouration

Warning coloration in some Lepidoptera caterpillars and other insects to deter predators.