1. Entomology 101 Orders of Insects
David J. Shetlar, Ph.D.
The “BugDoc”
The Ohio State University,
OARDC & OSU Extension
Columbus, OH
© Sept, 2009, D.J. Shetlar, all rights reserved

2. Class Hexapoda Three tagmata – head, thorax, abdomen
(the insects)
Three tagmata – head, thorax, abdomen
Thorax with three pairs of legs; normally two pairs of wings in adult stage
Head with one pair of antennae
Respiration by trachea
Terrestrial & fresh water inhabitants

3. Class Hexapoda Life Cycle Groups
(all have one pair of antennae, a head, thorax & abdominal regions, three pair of legs, adults usually have wings, use trachea)
Life Cycle Groups
Simple Metamorphosis (=incomplete) - egg, nymph, adult stages
Complete Metamorphosis - egg, larva, pupa, adult stages

4. Incomplete Metamorphosis Example
(hairy chinch bug)
egg st nd rd th th adult
instar instar instar instar instar
Egg Nymphal Adult
Stage Stage Stage

5. Incomplete Metamorphosis Example
(hairy chinch bug)
egg 1st nd rd th th normal wing short wing
instar instar instar instar instar adult adult
Egg Nymphal Adult
Stage Stage Stage

6. Complete Metamorphosis Example
(May/June beetle)
egg st nd rd pupa adult
instar instar instar
Egg Larval Pupal Adult
Stage Stage Stage Stage

7. Complete Metamorphosis Example
(northern masked chafer)
egg st nd rd pupa adult
instar instar instar
Egg Larval Pupal Adult
Stage Stage Stage Stage

8. Hexapod Orders Entognathous Hexapods – (simple metamorphosis cont’d)
Order Protura
Order Collembola
Order Diplura
Ectognathous apterygote Hexapods –
Order Microcoryphia
Order Thysanura
Pterygote Hexapods –
(simple metamorphosis)
Order Ephemeroptera
Order Odonata
Order Orthoptera
Order Phasmatodea
Order Dermaptera
Order Plecoptera
Order Isoptera
(simple metamorphosis cont’d)
Order Mantodea
Order Blattodea
Order Hemiptera
Order Thysanoptera
Order Psocoptera
Order Phthiraptera
(complete metamorphosis)
Order Coleoptera
Order Neuroptera
Order Hymenoptera
Order Trichoptera
Order Lepidoptera
Order Siphonaptera
Order Diptera

9. Orders of Insects
(no metamorphosis)
Some consider these groups insect-like and place in different class or subclass.
Adults do not have wings and may molt after becoming mature
Thysanura - silverfish, firebrats
Collembola - springtails

10. Order Thysanura (=bristle tail) silverfish & firebrats
Look like they have 3 tails –
2 cerci
1 median filament
Wingless (originally)
Most are covered with scales
Chewing mouthparts
Gradual (no) metamorphosis
Feed on organic matter & starches

11. Thysanura (=bristletail)
(silverfish, firebrats; 0.4K spp.)
[no wings as adults, usually 3 caudal appendages (two cerci and median filament); adults may continue to molt]
Silverfish
Fourlined silverfish

12. Order Collembola (=glue wedge) springtails
Wingless (primitively)
Chewing mouthparts
Gradual (no) metamorphosis
Adults continue to molt
Feed on plants, bacteria, & fungi
Important as decomposers and bioindicators

13. Order Collembola (=glue wedge) springtails
Tiny, most < 3 mm
Collophore
Water regulatory structure
Underside 1st abdominal segment
Furcula
Forked jumping appendage
Underside 4th abdominal segment
Held bent under body
Escape by catapulting

14. Collembola (=glue wedge)
(springtails; >6K spp.)
[no wings as adults, caudal appendage designed for jumping (furcula & colliphore); adults may molt]
Springtail with furcula exposed.
Globular springtail, upper and lower views, spots on head are not eyes! Eyes are lower on head.

15. Aquatic springtails have waxy hairs that allow them to float on the water surface. These springtails feed on algae.
Springtails often have long hairs and multicolored scales.

16. (simple metamorphosis)
Orders of Insects
(simple metamorphosis)
Ephemeroptera - mayflies, shadflies
Odonata - dragonflies, damselflies
Orthoptera - grasshoppers, crickets, katydids
Dermaptera – earwigs
Plecoptera - stoneflies
Isoptera - termites

17. Order Ephemeroptera (=short lived, on the wing) Mayflies
Nymphs (naiads) aquatic
Wings triangular, held over back
Front wings large, usually with many veins
Hind wings small or absent
Adults with 2 or 3 long caudal filaments
Last instar nymph flies from water (subimago)
Adults live for hours to a few days.

18. Ephemeroptera (=short lived on the wing)
(Mayflies, shadflies, Canadian soldiers; 2K spp.)
[front wings large, triangular, held over body at rest; hind wings small or absent; aquatic nymphs with abdominal gills; caudal appendages (2 or 3) long; chewing mouthparts often non-functional in adult]
Mayfly adults, one two-tailed and one three-tailed.
Mayfly naiad.

19. Hexagenia, large Mayfly, subimago (last instar nymph)
Hexagenia, large Mayfly, subimago (last instar nymph). Note cloudy wings and short tails.
Hexagenia adult. Note clear wings and long tails.

20. Order Odonata (=toothed – large mandibles) Dragonflies and Damselflies
Front & Hind Wings narrow
Many veins and cross veins
Dragonflies hold wings out at rest
Damselflies hold wings over back
Nymphs (naiads) aquatic
Naiads predatory, have grasping mouthparts
Dragonfly naiads have rectal gills
Damselflies have leaflike gills on abdomen tip.
Adults are beneficial predators.

21. (dragonflies and damselflies; 5K spp.)
Odonata (=toothed)
(dragonflies and damselflies; 5K spp.)
[front and hind wings narrow with many cross veins, membranous; aquatic nymphs (naiads) predatory with caudal or rectal gills; antennae bristlelike, no abdominal cerci; chewing mouthparts]

23. Damselfly details

24. Order Orthoptera (=straight wing) grasshoppers & crickets
Two pairs wings
Forewings leathery & narrow; protect
Hindwings membranous, fan-folded
Some are wingless (cave crickets)
Most have hind legs enlarged for jumping
Females have prominent ovipositor
Produce songs by rubbing wing bases together or rubbing the wings on their legs

25. Order Orthoptera (straight wing) grasshoppers & crickets
Chewing mouthparts
Gradual metamorphosis
Antennae short or long
Most feed on plants
Some feed on organic matter, stored products; few predatory

26. Orthoptera (=straight wing)
(grasshoppers, crickets, Katydids; >20K spp.)
[front wings leathery, hind wings folded like a fan, chewing mouthparts, two cerci - usually short]

27. Mating pair of grasshoppers

28. Female cone-nose grasshopper

29. Black field cricket

30. Order Dermaptera (=skin wing) earwigs
Chewing mouthparts
Gradual metamorphosis
Omnivorous
Mostly scavengers
Occasional pests of plants
Nuisance pest in homes

31. Order Dermaptera (=skin wing) earwigs
Cerci shaped like forceps, pinchers
Defense, prey capture, mating
Elongate, flattened
Two pairs of wings
Forewings usually short, hard
Hindwings membranous, folded
Few species are wingless

32. Dermaptera (=skin wing)
(earwigs; 1.8K spp.)
[front wings short, leathery; hind wings double folded; abdominal cerci forceps-like; chewing mouthparts]
Seashore earwig adult
European earwig with eggs

33. Order Plecoptera (=folded wing) Stoneflies
Nymphs Aquatic (naiads)
Abdominal &/or thoracic gills
Predators & herbivores
Flat with obvious cerci
Chewing Mouthparts
Adults with
Front wing narrow, bladelike
Hind wing broad, flolded
Medium to long cerci
Good indicators of water quality

34. Plecoptera (=folded wing)
(stoneflies; 2K spp.)
[front wings narrow; hind wings folded fanlike; aquatic nymphs (naiads) with abdominal gills; abdominal cerci straight, moderately long; chewing mouthparts]

35. Giant Stonefly Adult

36. Order Isoptera (equal wing) termites
Social
Reproductives (queens & kings)
Four wings of equal size
Wings twice the length of the body
Wings lack cross-veins
Workers & soldiers
Lack wings
Body white
Distinguish from ants:
Lack of elbowed antennae
No constriction between abdomen & thorax

37. Order Isoptera (=equal wing) termites
Chewing mouthparts
Gradual metamorphosis
Feed on wood and plant materials
Protozoans digest cellulose
Significant structural pest
Build distinctive nests

38. Isoptera (equal wing) (termites; >2.3K spp.)
[social insects, winged reproductives with both wings same size and membranous; straight or curved antennae consists of beadlike segments; abdomen broadly joined to thorax; one to two-segmented cerci; chewing mouthparts]

39. Subterranean termite queen, king, workers and soldier

40. Nasutiform termite nest in tree.
Nasutiform soldiers protecting opened nest.

41. (incomplete metamorphosis cont’d)
Orders of Insects
(incomplete metamorphosis cont’d)
Mantoidea – mantids
Blattodea – cockroaches
Hemiptera - true bugs & bug-like insects
Thysanoptera - thrips
Psocoptera - barklice, booklice
Phthiraptera - biting & sucking lice

42. Order Mantodea (=soothsayer) mantids / praying mantid
Large ( mm)
Forelegs modified for grasping prey
Predatory
Chewing mouthparts
Gradual metamorphosis

43. Mantodea (=soothsayer)
(mantids, praying mantis; ~1.8K spp.)
[front legs raptorial (modified for grasping), prothroax elongated, chewing mouthparts, two short cerci]

44. Order Blattodea (=L. cockroach) cockroaches
Flattened body
Long slender antennae
Wings thickened, leathery
Wings reduced in some species
Legs modified for running
Chewing mouthparts
Gradual metamorphosis
Feed on organic matter, stored products, plants

45. Blattodea (L. cockroach)
(cockroaches; <4K spp.)
[body flattened and oval, front wings leathery, hind wings folded like a fan, chewing mouthparts, two short cerci]

46. Order Hemiptera (=half wing) true bugs & bug-like insects
Formerly 2 separate orders; recently combined
Suborder Heteroptera
Suborders Auchenorrhyncha & Sternorrhyncha (former Homoptera)

47. Suborder Heteroptera the true bugs
Piercing/sucking mouthparts
Prominent beak arises from front of head
Two pairs of wings on most
Forewings: thickened front halves
Hindwings: membranous
Forewings lay flat, overlapping
Scutellum (▼-shaped)

48. Suborder Heteroptera true bugs
Many have scent glands
Plant feeders, predators, blood feeders
Gradual metamorphosis

49. Hemiptera (s.o. Heteroptera)
(half wing) (true bugs; 23K spp.)
[front wings half leathery & half membranous; hind wings membranous; usually long antennae; sucking mouthparts arise from front of head]

52. Suborder Auchenorrhyncha leafhoppers, cicadas & Suborder Sternorrhyncha aphids,whiteflies, scales, psyllids, mealybugs
Piercing/sucking mouthparts
Beak arises from rear underside of head

53. Suborders Auchenorrhyncha & Sternorrhyncha
Wings:
Uniformly textured
Some have 4 wings
Some have 2 wings (in males of some species)
Some have no wings
Wings often held roof-like over the body

54. Suborders Auchenorrhyncha & Sternorrhyncha
Gradual metamorphosis
All are plant feeders
Many are vectors of plant disease

55. Hemiptera (s.o. Auchenorrhyncha)
(buglike insects: cicadas, leaf, plant & tree hoppers; 33K spp.)
[front wings same texture throughout, leathery or membranous (wings often absent); long or bristlelike antennae; sucking mouthparts arise from back of head or between front legs]

56. Hemiptera (s.o. Sternorrhyncha)
(buglike insects: psyllids, whiteflies, aphids, mealybugs, & scales)

57. Order Thysanoptera (=fringe wing) thrips (singular & plural!)
Small (most <4 mm), elongate
Chewing mouthparts
Small conical beak
Rasping mouthparts
Most with 4 wings
Strap-like
Fringed with long bristles
Some species are wingless

58. Order Thysanoptera (=fringe wing) thrips
Plant feeders or predators
Flowers are favored
Gradual metamorphosis but more intermediate: egg, larva, prepupa, pupa, adult
Thrips: only plural form of word!

59. Thysanoptera (=fringe wing)
(thrips; 4.5K spp.)
[small; front and hind wings bladelike with hair fringe, often absent; mouthparts modified rasping sucking; antennae short]

61. Order Psocoptera (=rub wings) psocids, booklice, barklice
Small, soft-bodied
Front of head bulging
Wings present or absent
Reduced veins when present
Often reduced (brachypterous)
Chewing mouthparts
Eat molds & mildews
Barklice feed on lichens

62. Psocoptera (=rub small wing)
(psocids, booklice, barklice; >3K spp.)
[front wings with reduced venation; hind wings reduced or absent; wings often absent; distinctive frontal bulge on head; long antennae; chewing mouthparts; booklice are extremely flattened]

63. Order Phthiraptera (=lice without wings)
Formerly 2 separate orders
Suborder Mallophaga (wool eater): chewing lice
Suborder Anoplura (unarmed tail): sucking lice

64. Order Phthiraptera (=lice without wings), Suborder Mallophaga (=wool eater) chewing lice
Small, hard, dorso-ventrally flattened
Wingless
Chewing mouthparts
Head usually broadly rounded & wider than prothorax
Gradual metamorphosis
Feed mostly on birds, some mammals

65. Phthiraptera (Mallophaga)
(lice without wings) (biting lice; 2.7K spp.)
[very flat, small; no wings; chewing mouthparts; external parasites of birds and mammals]
Chicken biting louse

66. Biting louse adult (above) and eggs (right) on goose feathers.

67. Order Phthiraptera (=lice without wings), Suborder Anoplura (=unarmed tail) sucking lice
Small, hard, dorso-ventrally flattened
Wingless
Piercing/sucking mouthparts
Head narrower than prothorax
Suck blood of mammals
Gradual metamorphosis

68. Phthiraptera (Anoplura)
(sucking lice; 0.3K spp.)
[small, flattened; no wings; sucking mouthparts; external parasites of mammals]
Human head louse
Human crab louse