BIO 385 — Invertebrate Zoology
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Invertebrate Diversity
Phylum Arthropoda
Class Insecta

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Insecta Characteristics

  • Body with three distinct tagmata: head; thorax (with 3 pairs of legs); & abdomen
  • Direct or indirect development:
    • Ametabolous (direct) development = young are identical to adults except for size, gonads; only in primitive wingless insects and entognaths
    • Hemimetabolous (direct) development = nymphs (or naiads if aquatic) generally similar to adults, but wingless; do not undergo complete metamorphosis
    • Holometabolous (indirect) development = larvae very different from adults, require complete metamorphosis via pupal stage
  • Mouthparts external (usually visible)
  • Most with either hemimetabolous or holometabolous development
  • Most have 2 pairs of wings (a few are primitively wingless and some are secondarily wingless)
  • Eyes and other sensory structures well developed
  • Most diverse class; nearly 1 million species described (with at least several million more awaiting discovery!)
  • 33 Orders

Tomocerus nigritus
Ametabolous Development
Springtails, Tomocerus nigritus: adult (left) & nymph (upper right)
Large Milkweed Bug
Hemimetabolous Development
Large Milkweed Bug, Oncopeltus fasciatus: nymphs and adult
Cabbage Looper Moth
Holometabolous Development
Cabbage Looper Moth, Trichoplusia ni: larva, pupa, and adult

See also Insect Coloration Page


Class Insecta


Apterygota* — Primitively wingless insects

Order Archaeognatha

  • Jumping bristletails
  • Primitively wingless; ametabolous development
  • 3 posterior filaments
  • Arched (humped) back
Bristletail
Jumping Bristletail; KY
Jumping Bristletail
Jumping Bristletail; MT

Order Zygentoma

  • Silverfish & firebrats
  • Primitively wingless; ametabolous development
  • 3 posterior filaments
  • Dorsoventrally flattened
  • Silvery scales
Bristletail
Firebrat, Thermobia domestica; CA
Gray Silverfish
Gray Silverfish, Ctenolepisma longicaudata; AZ
Common Silverfish
Common Silverfish, Lepisma saccharina?; AZ

Subclass Pterygota (all winged insects) — Subgroup Palaeoptera* (lack ability to fold wings flat over back)

Order Ephemeroptera

  • Mayflies
  • Wings held vertically over back
  • Hindwings much smaller than forwings (sometimes absent)
  • Back is often held in concave arch
  • 2 elongated tail streamers (cerci)
  • Naiads are aquatic
Stream Mayfly
Stream Mayfly, family Heptageniidae; UT
Mayfly Naiad
Stream Mayfly Naiad, family Heptageniidae; AZ

Order Odonata

  • Dragonflies & damselflies
  • Do not fold wings flat over body
  • Large mandibles and eyes
  • Hemimetabolous: nymphs are aquatic (called naiads)
Widow Skimmer
Widow Skimmer, Libellula luctuosa, a dragonfly; KY
Spreadwing
Great Spreadwing, Archilestes grandis, a dragonfly (family Lestidae); AZ
Dragonfly Naiad
Dragonfly Naiad; AZ
Rubyspot
American Rubyspot, Hetaerina americana, a damselfly; CA
Desert Firetails
Male & female Desert Firetails, Telebasis salva, damselflies (family Coenagrionidae); AZ
Damselfly Naiad
Exuvium (shed exoskeleton) of a damselfy naiad; CA

Clade Neoptera (can fold wings flat) — Subgroup Exopterygota*

Order Plecoptera

  • Stoneflies
  • Wings membranous, with complex venation
  • Chewing mouthparts
  • Pair of long cerci at end of abdomen
  • Naiads are aquatic
Green Stonefly
Green Stonefly (family Chloroperlidae); PA
Stonefly Naiad
Stonefly Naiad (Order Plecoptera); PA

Order Embioptera

  • Webspinners
  • Males have wings; females wingless
  • Spin silk from forelimbs to line burrows
  • Body cylindrical
  • Enlarged, bulging tarsus on forelimb
  • Cerci present
Webspinner
Black Webspinner, Oligotoma nigra, male; AZ (introduced)
female Webspinner
Black Webspinner, Oligotoma nigra, female; AZ
Nymph Webspinner
Black Webspinner, Oligotoma nigra, nymph; AZ

Order Phasmatodea

  • Stick insects, walking sticks
  • Highly elongated bodies with long legs
  • Generally resemble sticks or leaves
Walkingstick
Northern Walkingstick, Diapheromera femorata, male; NY
Prairie Walkingstick
Prairie Walkingstick, Diapheromera velii, NM
Spiny StickInsect
Giant Spiny StickInsect, Eurycantha calcarata

Order Orthoptera

  • Grasshoppers & crickets
  • Hind legs elongated for jumping
  • Forewings leathery
  • Chewing mouthparts (herbivores)
  • Males frequently stridulate (produce sound)
  • Tympanic membranes (hearing) present
Grasshopper
Gaudy Grasshopper, Taphronota sp.; Kenya
See also labeled photo.
Sagebrush Grasshopper
Sagebrush Grasshopper, Melanoplus bowditchi (family Acrididae); NY
Grasshopper Nymph
Spur-throated Grasshopper nymph, Melanoplus sp.?; AZ
See also labeled photo.
Bush Katydid
Elegant Bush Katydid, Insara elegans, female (family Tettigoniidae)
Katydid Nymph
Unidentified Katydid nymph (family Tettigoniidae); AZ
House Cricket
Indian House Cricket, Gryllodes supplicans; AZ

Order Blattodea

  • Roaches & Termites
  • Dorso-ventrally flattened
  • Forewings leathery or wings absent
  • Chewing mouthparts (except some termites)
  • Pair of cerci at end of abdomen
  • Termites specialized for eating cellulose:
    • Eusocial: live in colonies
    • Multiple castes, typically with reproductives, soldiers, workers
    • Alates (new reproductives) have 2 pairs of long membranous wings; all other castes wingless
Wood Cockroach
Wood Cockroach, Parcoblatta sp.; KY
hissing cockroach
Madagascar Hissing Cockroach, Gromphadorhina portentosa
White cockroach
Unidentified Cockroach, recently molted; AZ
Termites
Termites, including queen, king, workers (gray), and nymphs (white); Kenya
Subterranean Termite Alates
Eastern Subterranean Termite alates & soldier, Reticulitermes flavipes; KY
Nasute Termites
Nasute Termite soldiers, Nasutitermes sp. Their head is modified into a nozzle that squirts a sticky glue on their attackers; Belize.

Order Mantodea

  • Mantids
  • Large raptorial forelegs
  • Triangular heads with large eyes
  • Leathery forewings cover hindwings at rest
  • Ambush predators
Flower Mantid
Common Spiny Flower Mantid, Pseudocreobotra wahlbergi; Kenya
Minor Ground Mantid
Minor Ground Mantid, Litaneutria minor; AZ
Horned Mantid
Gargoyle Mantid nymph, Idolomorpha sp.; Kenya.

Order Dermaptera

  • Earwigs
  • Elongated, flattened body
  • Enlarged cerci form posterior pincer
  • Wings small: hindwings hidden under pad-like forewings
European Earwig
European Earwig, Forficula auricularia; KY
Ringlegged Earwig
Ring-legged Earwig, Euborellia sp.; AZ
Earwig Nymph
Nymph of an unidentified earwig (family Forficulidae); AZ.

Order Hemiptera

  • True Bugs, hoppers, aphids, etc.
  • Sucking beak tucked underneath body
  • Base of forewings leathery (true bugs) or entire wing membranous
Leaf-footed Bug
Leaf-footed Bug, Acanthocephala terminalis; KY
Assassin Bug
Assassin Bug, Pselliopus sp.; AZ
Periodic Cicada
Assasin Bug nymph; AZ
Waterscorpion
Waterscorpion, Ranatra sp.; AZ
Stink Bug
Twice-stabbed Stink Bug, Cosmopepla lintneriana; KY
Periodic Cicada
17-Year Periodic Cicada, Magicicada cassini; KY
Aphids
Oleander Aphids, Aphis nerii; AZ
Treehopper & Ant
Treehopper, Entylia carinata, attended by ant; NY
Treehopper
Oak Treehopper, Platycotis vittata; KY

Other Orders of the Exopterygota

  • Phthiraptera: lice
    • Wingless, flattened, external parasites
  • Thysanoptera: thrips
    • Tiny (≤ 1 mm) plant-feeding insects with wings fringed by hairs
Louse
Human Body Louse, Pediculus humanus (Order Phthiraptera)
Thrip
Thrip (Order Thysanoptera)
Thrips
Thrips (Order Thysanoptera) on desert poppy petal; AZ.

Clade Endopterygota

Order Neuroptera

  • Lacewings, antlions, owlflies, etc.
  • Both pairs of wings similar in size
  • Wings heavily veined with many cross-veins
  • Relatively soft-bodied and delicate
  • Larvae are mostly predators (antlions dig pits to trap ants)
Lacewing
Green Lacewing, Chrysoperla sp.?; AZ
Mantidfly
Mantidfly, Plega signata; collected in AZ
Owlfly
Ascalaphine Owlfly; Kenya
Antlion
Antlion, Myrmeleon sp.; AZ
Antlion larva
Antlion larva, dried specimen; AZ

Order Megaloptera

  • Alderflies & dobsonflies
  • Resemble the neuroptera, but have creased hind wings
  • Typically have very large mandibles
  • Larvae are aquatic
Dobsonfly
Western Dobsonfly, Corydalus texanus, female; AZ
Alderfly
Nearctic Alderfly, Sialis sp.; PA

Order Coleoptera

  • Beetles
  • Forewings hardened into elytra that cover abdomen & form seam along body midline
  • General chewing mouthparts
  • Largest order; >350,000 species
  • Larvae are often referred to as grubs
Glorious Beetle
Glorious Beetle, Chrysina gloriosa
Tiger Beetle
Six-spotted Tiger Beetle, Cicindela sexguttata, eating ant; KY
Billbug
Billbug, Sphenophorus sp.; AZ
Powderpost Beetle
Horned Powderpost Beetle, Apatides fortis; AZ
Banded Netwing
Banded Net-wing, Calopteron terminale; KY
Diving Beetle
Sunburst Diving Beetle, Thermonectus marmoratus
Hercules Beetles ad & larva
Eastern Hercules Beetles, Dynastes tityus, adult male and larva
Lady Beetle
Convergent Lady Beetle, Hippodamia convergens; AZ
Lady Beetle Larva
Lady Beetle larva; AZ

Giraffe Weevil M & F
Giraffe Weevils, Trachelophorus sp., male (top) and female (lower left) dried specimens

Order Trichoptera

  • Caddisflies
  • Somewhat mothlike
  • Wings covered in hairs, held tent-like over body
  • Antennae usually very long
  • Larvae aquatic, make cases
Giant Casemaker
Giant Casemaker, Ptilostomis sp.; KY
Mottled Caddisfly
Mottled Caddisfly, Hydropsyche sp.; AZ
Mortarjoint Casemaker
larva and case of Mortarjoint Casemaker Caddisfly (family Odontoceridae); NE

Order Lepidoptera

  • Butterflies & moths
  • Wings broad, covered in scales
  • Coiled, sucking mouthparts
  • Larvae are called caterpillars
Io Moth
Io Moth, Automeris io; KY
Ash Sphinx
Great Ash Sphinx Moth, Sphinx chersis; AZ
Caterpillar
Sphynx Moth Caterpillar, Manduca sp.; AZ
Pale Swallowtail
Pale Swallowtail, Papilio eurymedon; CA
MonarchButterfly
Monarch Butterfly, Danaus plexippus; NJ
MonarchCaterpillar
Monarch Butterfly Caterpillar, Danaus plexippus; AZ
Skipper
Taxiles Skipper, Poanes taxiles; AZ
Plume Moth
Himmelman's Plume Moth, Geina tenuidactyla; NY
FlannelMothCaterpillar
Southern Flannel Moth Caterpillar, Megalopyge opercularis; KY

Orders Mecoptera* (& Siphonaptera)

  • Scorpionflies & hangingflies
  • Superficially fly-like, but with 4 long, membranous wings
  • Rostrum (snout) elongated
  • The Siphonaptera (fleas) are derived from within the Mecoptera
    • Wingless external parasites of mammals and birds
    • Body laterally compressed
    • Extremely long jumping hind legs
    • Proboscis for sucking blood
Scorpionfly
Scorpionfly, Panorpa sp. (Order Mecoptera); KY
Hangingfly
Black-tipped Hangingfly, Hylobittacus apicalis; KY
Flea
Cat or Dog Flea, Ctenocephalides sp. (Order Siphonaptera)

Order Diptera

  • True flies
  • Hind wings absent (reduced to club-like halteres)
  • Sucking or sponging mouthparts
  • Mobile head with large eyes
  • Larval types include maggots and aquatic forms
Dung Fly
Golden-haired Dung Fly, Scathophaga stercoraria; CA
Crane Fly
Crane Fly, Tipula sp.; AZ
Tachinid Fly
Tachinid Fly, Belvosia sp.; AZ
Robber Fly
Robber Fly, Efferia sp.?; AZ
Flower Fly
Flower Fly, Toxomerus marginatus; AZ
Fly Maggot
Unidentified Fly Maggot in rotting cactus; AZ
Mosquito
Mosquito, Ochlerotatus sp., female; NM
Green Midge
Green Midge, Tanytarsus sp. (family Chironomidae); PA
Midge Larva
Chironomid Midge Larva, Toxomerus marginatus (aquatic); AZ

Order Hymenoptera

  • Bees, wasps, ants
  • Hindwings smaller than and hook to forewing
  • Ovipositer modified for piercing, stinging
  • Typically have narrow "waist" between thorax and abdomen
  • Social behavior, including eusociality, is common (but not universal)
Spider Wasp
Spider Wasp, Priocnemis minorata; larvae feed on immobilized spiders; NY
Bee
Leaf-cutting Bee, Megachile sp.; CO
Metallic Green Bee
Metallic Green Bee, Agapostemon sp.; UT
Ichneumonid wasp
Short-tailed Ichneumon, Ophion sp.; larvae are parasitic on caterpillars; AZ
Gall Wasp Larva
Oak Apple Gall Wasp larva in cut gall, Amphibolips confluenta; KY
Honey Bees
European Honey Bee, Apis mellifera, swarm; many hymenopterans are eusocial; AZ
Mud Dauber
Black-and-yellow Mud Dauber, Sceliphron caementarium; AZ
Leaf-cutter Ant
Leaf-cutter Ant, Atta cephalodes; Belize
Carpenter Ants
Black-headed Carpenter Ant, Camponotus ocreatus nest with larvae, pupae & 2 worker castes; AZ

* = indicates a paraphyletic group
This page last updated 4 June 2022 by Udo M. Savalli ()
Images and text © Udo M. Savalli. All rights reserved.