BIO 385 Invertebrate Zoology
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Invertebrate Diversity
Phylum Arthropoda
Superclass Hexapoda

Return to Main Arthropod Page

Hexapod Characteristics

  • Body with three distinct regions: Head (5 segments); Thorax (3 segments); & Abdomen (11 segments)
  • 3 pairs of uniramous legs (on thorax)
  • Trachea (respiration)
  • Malphigian tubules (excretion)
  • Most species have 2 pairs of wings; capable of flight
  • Direct (hemimetabolous; with adult-like nymphs) or indirect (holometabolous, with distinct larval stage) development

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

Class Entognatha

  • Mouthparts enclosed within head (not externally visible)
  • Ametabolous development (no structural differences between juveniles and adults)
  • All are wingless
  • Eyes reduced or absent
  • Most live in soil
  • 3 Orders

Order Collembola

  • Springtails
  • Furcula: abdominal jumping appendage
  • Small size, <6 mm
Springtail, Tomocerus nigritus; NY
White Springtail
Springtail, possibly Cyphoderus similis; AZ
Springtail, whole mount slide

Class Insecta

  • 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

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
American Rubyspot, Hetaerina americana, a damselfly; CA
Dragonfly Naiad
Dragonfly Naiad; AZ

Order Orthoptera

  • Grasshoppers & crickets
  • Hind legs elongated for jumping
  • Forewings leathery
  • Chewing mouthparts (herbivores)
  • Males frequently stridulate (produce sound)
  • Tympanic membranes (hearing) present
  • Hemimetabolous
Leaf-mimicking Katydid; Kenya
Gaudy Grasshopper, Taphronota sp.; Kenya
See also labeled photo.
House Cricket
Indian House Cricket, Gryllodes supplicans; AZ

Order Blattodea

  • Roaches
  • Dorso-ventrally flattened
  • Forewings leathery (or wings absent)
  • Chewing mouthparts
  • Pair of cerci at end of abdomen
  • Hemimetabolous
Wood Cockroach
Wood Cockroach, Parcoblatta sp.; KY
hissing cockroach
Madagascar Hissing Cockroach, Gromphadorhina portentosa
White cockroach
Unidentified Cockroach, recently molted; AZ

Order Isoptera

  • Termites
  • Specialized for eating cellulose
  • All are eusocial; live in colonies
  • Multiple castes, typically with reproductives, soldiers, workers
  • Alates (new reproductives) have 2 pairs of long membranous wings
  • All other castes are wingless, soft-bodied and usually pale colored
  • Eyes poorly developed
  • Hemimetabolous
Termites, including queen, king, workers, and nymphs; 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
  • Hemimetabolous
Flower Mantid
African Flower Mantid, Pseudocreobotra wahlbergi; Kenya
Minor Ground Mantid
Minor Ground Mantid, Litaneutria minor; AZ
Horned Mantid
Cone-headed Mantid nymph, Idolomorpha dentrifrons; Kenya.

Order Hemiptera

  • True Bugs, hoppers, aphids, etc.
  • Sucking beak tucked underneath body
  • Base of forewings often leathery
  • Hemimetabolous
Leaf-footed Bug
Leaf-footed Bug, Acanthocephala terminalis; KY
Stink Bug
Twice-stabbed Stink Bug, Cosmopepla lintneriana; KY
Periodic Cicada
17-Year Periodic Cicada, Magicicada cassini; KY

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
  • Holometabolous
Antlion, Myrmeleon sp.; AZ
Mantidfly, Mantispa sp.; collected in AZ
Green Lacewing, Chrysoperla sp.?; AZ

Order Coleoptera

  • Beetles
  • Forewings hardened into elytra that cover abdomen & form seam along body midline
  • General chewing mouthparts
  • Largest order; >350,000 species
  • Holometabolous: larvae are often grubs
Glorious Beetle
Glorious Beetle, Chrysina gloriosa
Tiger Beetle
Six-spotted Tiger Beetle, Cicindela sexguttata, eating ant; KY
Billbug, Sphenophorus sp.; AZ

Order Diptera

  • Hind wings absent (reduced to club-like halteres)
  • Sucking or sponging mouthparts
  • Mobile head with large eyes
  • Holometabolous: larval types include maggots
Dung Fly
Golden-haired Dung Fly, Scathophaga stercoraria; CA
Crane Fly
Crane Fly, Tipula sp.; AZ
Flower Fly
Flower Fly, Toxomerus marginatus; AZ

Order Lepidoptera

  • Butterflies & moths
  • Wings broad, covered in scales
  • Coiled, sucking mouthparts
  • Holometabolous: larvae are caterpillars
Pale Swallowtail
Pale Swallowtail, Papilio eurymedon; CA
Io Moth
Io Moth, Automeris io; KY
Sphynx Moth Caterpillar, Sphinx sp.; AZ

Order Hymenoptera

  • Bees, wasps, ants
  • Hindwings reduced, hook to forewing
  • Ovipositer modified for piercing, stinging
  • Typically have narrow "waist"
  • Holometabolous
Spider Wasp
Spider Wasp, Priocnemis minorata; NY
Leaf-cutting Bee, Megachile sp.; CO
Leaf-cutter Ant
Leaf-cutter Ant, Atta cephalodes; Belize

Other Insect Orders

  • Recognize as insects, but don't need to know these orders
Jumping Bristletail (Order Archaeognatha), a primitive wingless insect; KY
Firebrat, Thermobia domestica (Order Zygentoma [=Thysanura]), a primitive wingless insect; CA
Stream Mayfly
Stream Mayfly (Order Ephemeroptera); UT
European Earwig
European Earwig, Forficula auricularia (Order Dermaptera); KY
Northern Walkingstick, Diapheromera femorata, male (Order Phasmida); NY
Stonefly Naiad
Stonefly Naiad (Order Plecoptera); PA
Black Webspinner, Oligotoma nigra, male (Order Embioptera); AZ
Western Dobsonfly, Corydalus texanus, female (Order Megaloptera); AZ
Giant Casemaker
Giant Casemaker, Ptilostomis sp. (Order Trichoptera); KY
Scorpionfly, Panorpa sp. (Order Mecoptera); KY
Thrip (Order Thysanoptera)
Cat or Dog Flea, Ctenocephalides sp. (Order Siphonaptera)

This page last updated 30 December 2014 by Udo M. Savalli ()
Images and text Udo M. Savalli. All rights reserved.