This document provides information on the characteristics of arthropods including insects and their relatives. It discusses key traits such as an exoskeleton, undergoing metamorphosis, and molting. Specific orders are examined, including beetles, earwigs, flies, true bugs, bees/wasps, butterflies/moths, thrips, grasshoppers/crickets and mites. Each order's traits such as mouthparts, wings, body structure and life cycles are described.

1. Arthropods
Insects and their relatives

2. Insects and Their Relatives
Characteristics
– Exoskeleton (external covering)
– Molts or sheds exoskeleton to grow
– Undergo metamorphosis or pass through a
number of distinct growth stages during
their lives

3. Metamorphosis
Simple or gradual
– three changes
• egg
• nymph
– 3-5 instars
• adult
– adults and nymphs
• eat same food

4. Metamorphosis
Complex or complete
– four changes
• egg
• larva
• pupa
• adult
– larvae and adults
• eat different food
– larvae are destructive

5. External structure
Insects
– 3 body regions
• head
• thorax
• abdomen
– 3 pair legs attached to thorax
– 1 pair antennae
– wings usually present in adult state.

6. External structure
Arachnids (spiders and mites)
– 2 body regions
• cephalothorax
• abdomen
– usually 4 pair legs
– no wings
– no antennae

7. Other Arthropods
Crustaceans Mollusca
– Pillbugs – snails
– Sowbugs – slugs
Pillbugs - photo J. Kalish -
UNL Gray garden slug photo
Ohio State University

8. Other Arthropods
Diplopoda Chilopoda
– Millipedes – Centipedes
Photo J. Kalish - UNL

9. Insect Orders

10. Beetles - Coleoptera
Largest order of insects (25,000 species
in North America)
Many species are plant feeders, some
are predaceous (lady beetles)
The term weevil refers to a snouted
beetle

11. Beetles
Metamorphosis
– Complete or complex
Mouth parts
– Chewing (both adult and larvae)

12. Beetles - Adults
• Wing: 2 pair, the front pair (elytra) are
greatly thickened and shell-like and when
at rest meet in a straight line down the
back. Hind membranous wing pair is
protected by front pair.

13. Beetles - Larvae
Larvae that feed externally on plants are
typical “grub” with head capsule, 3 pair
of legs on the thorax, and no legs on the
abdomen

14. Beetles - Larvae
Larva that feed internally in plants (e.g.
bark beetles, weevils, woodborers)
typically lack legs.
Chewing mouthparts

15. Earwigs- Dermaptera
Introduced from Europe
Metamorphosis: gradual or simple
Mouthparts: chewing, general feeders
on decaying organic matter,
occasionally feed on plants and insects.
Can pinch with mouthparts.

16. Earwigs
Wings: 2 pair; front wings are short
leathery without venation and meet in a
straight line down the back when at rest.
Can be confused with those of beetles,
but beetles do not have forceps-like
cerci.

17. Earwigs
Body: Elongated, flattened
Cerci: Tail-like pinchers. The cerci on
males are bowed, while straight on
females. Cerci cannot produce a
painful pinch.
Habit: Over winters as adults. During
the day, earwigs like to hide in dark,
moist areas.

18. Flies, Gnats, Midges,
Mosquitoes- Diptera
Second only to beetles in number.
Feeding habits vary widely
– Scavengers (house flies, blow flies)
– Blood feeding (mosquitoes)
– Plant galls (gall midges)
– Predators (flower flies, robber flies)
– Aquatic

19. Flies, Gnats, Midges, Mosquitoes
If the fly is a Diptera, the name is written
as two words (house fly, deer fly). If the
fly is not a Diptera, the name is written
as one word (sawfly, butterfly, whitefly)

20. Flies, Gnats, Midges
Metamorphosis : Complete

21. Flies, Gnats, Midges -Adult
Wings: 1 pair of wings (an easy ID for
Diptera). Adults are typically soft
bodied and often hairy.
– Note: They may look like bees, wasps or
flies---count the wings! On many
Hymenoptera the wings may be attached
and the hind wings may be hidden under
the front wing.

22. Flies, Gnats, Midges- Adult
Mouthparts: highly variable
– Sponging (house fly)
– Cutting-lapping (horse fly)
– Piercing-sucking (mosquito)

23. Flies, Gnats, Midges - larvae
Vary greatly in Lower forms, such
appearance. Larva as mosquitoes, have
of advanced forms, a small head
like the house fly, capsule.
are maggot type
having mouth hooks
and not head
capsule or legs.

24. Hemiptera
True bugs: plant bugs, squash bugs, stink bugs
Order includes many important
predators.
If the bug is a Hemiptera the name is
written as two words (stink bug, water
bug, squash bug). If the insect is not a
Hemiptera, the name is written as one
word (ladybug)

25. True Bugs
Metamorphosis: gradual or simple
Mouthparts: piercing-sucking.
Mouthparts usually easily visible and
appears to arise from front of head,
ahead of eyes. By contrast Homoptera
mouthparts are not very visible and appear to arise
from the area between the front pair of legs.

26. True Bugs
Wings: 2 pair. Front wings (called
hemielytra) are thickened at base and
membranous at end, and overlap at tips
when at rest. Hind wings are
membranous. Nymphs have no wings,
but wing pads may be visible in older
nymphs.

27. True Bugs
Body: Usually broad and somewhat
flattened; a triangular plate (the
scutellum) is located between the base
of the wings.

28. Homoptera
Aphids, cicadas, leafhoppers, mealybugs
psyllids, scales, whitefiles
All species are plant Insects in this order
feeders, often are carriers
feeding on phloem (vectors) of several
sap. plant pathogens.
Excretion of honey
dew is common to honeydew
many members of
the order.

29. Aphids and Psyllids, etc
Metamorphosis: gradual; nymphs and
adults similar in appearance (except
scales and whiteflies)

30. Aphids and Psyllids, etc
Mouthparts: Piercing-sucking; jointed
beak-like mouthparts. Not very visible
and appear to arise from the area
between the front pair of legs. By contrast,
Hemiptera mouthparts are usually easily visible and
appear to arise from the front of the head, ahead of
the eyes.

31. Aphids and Psyllids, etc
Wings: 2 pair of
membranous wings;
generally held roof-
like over the body
when at rest. Many
wingless forms
occur. No wings on
nymphs, but wing
pads may be
observed on older
nymphs.

32. Hymenoptera
Ants, bees, horntails, sawflies, wasps
Order includes many important
parasites and predators.
The order has the most highly
developed insect behaviors and social
patterns.

33. Bees, Wasps, Sawflies
Metamorphosis: complete
Mouthparts: chewing or chewing-
sucking

34. Bees, Wasps, Sawflies - Adult
Wings: 2 pair membranous wings, often
hooked together. Hind pair are usually
smaller.
Mouthparts: typically chewing or
chewing-sucking

35. Bees, Wasps, Sawflies - Adult
Body: Adults are rather soft-bodied or slightly
hardened bodies. Most species have a
distinct constriction between the thorax and
abdomen (wasp waist). Exception: sawfly/horntail
group does not have the wasp waist.
Antennae: jointed sometimes elbowed.
Stinger: female abdomen usually provided
with a saw, piercing organ, or stinger.

36. Bees, Wasps, Sawflies - Larvae
Larva of most species are rarely
observed, often developing in a nest or
as an internal parasite.
Head: a distinct head capsule
Mouthparts: chewing

37. Bees, Wasps, Sawflies - Larvae
Legs: none (except some sawfly larva)
– Note: Sawfly larva may look like
caterpillars. Caterpillars have up to 5 pair
of prolegs on abdomen. Sawfly larvae
have 6+ pair prolegs on abdomen.

38. Lepidoptera
Butterflies, moths, skippers
Metamorphosis: complete
Mouthparts: coiled sucking tube
(lapping) as adults. Some adults don’t
feed at all. As larvae have chewing
mouthparts
Egg Mass
Cocoon Caterpillar
Butterfly

39. Butterflies, Moths, Skippers -
Adult
Wings: 2 pair often large, covered with
small overlapping scales, often but not
always brightly colored.
Black Swallowtail
Black swallowtail larva

40. Butterflies and Moths- Adults
Butterflies have slender bodies, the wings are
held vertical when at rest, and the antennae
are slender and club like at the tips. They are
day fliers.
Moths have stout bodies and wings are held
in a roof like horizontal position over the body
when at rest. Antennae are variable in form,
but usually filamentous of featherlike. Most
fly at night

41. Skippers - Adults
Skippers dart or skip through the air in
flight during the day. Their bodies are
intermediate in form, between the moths
and common butterflies. Their wings
are held erect when at rest. The
antennae of skippers are club-like at the
tips, and often have hook-like ends of
the club or knob.

42. Lepidoptera larvae:
Caterpillars
Legs: 3 pair of legs on thorax
Prolegs: Up to 5 pair of prolegs (fleshy
leg-like structure with hook-like crochets
on the end) on some abdominal
segments.)
– Note: Sawfly larvae look like smooth
bodied caterpillars but have more than 5
pair of prolegs on the abdomen. Their
bodies also taper from the head.

43. Caterpillars
Decorations: Often highly colored or
decorated with spines or other
appendages.
Mouthparts: Chewing mouthparts with
voracious appetites.
Variegated
Fritillary Larva
Variegated Fritillary Adult

44. Thysanoptera
Thrips
Very common insects, but due to the
tiny size are rarely observed.
Feeding leaves the plant looking
scarred, as they rasp the leaf or flower
surface and suck plant fluids.
Thrips

45. Thrips
Metamorphosis: a variation of gradual
Mouthparts: rasping-sucking
Wings: 4 (2 pair) slender wings fringed
with hairs, often absent.
Tarsi: Feet are 1 or 2 segmented, each
with a balloon-like structure on the end.
Size: minute, less than 1/8 inch long.

46. Orthoptera
Crickets, grasshoppers, katydids
Most are plant feeders. A few are
predators.
Note: Some books place Mantodea
(mantids), Phasmida (walking sticks)
and Blattaria (roaches) in the order
Orthoptera.

47. Grasshoppers and Crickets
Metamorphosis Gradual
Mouthparts: chewing
Wings: Usually have 2 pair of wings.
Front wings more or less parchment-like
with distinct venations. Wings may
overlap at rest. Wings may be used to
make sounds.

48. Grasshoppers and Crickets
Legs: Hind legs designed for jumping.
Antennae: thread-like.
Cerci: 1 pair tail-like appendages on
most adults.

49. Insect relatives - Mites
Two body segments 8 legs.
Tiny soft- bodied organisms that appear
almost everywhere.
Adult and immatures have sucking
mouthparts
Two types
Spider mites
– spider mites
– eriophyid mites

50. Mites
Foliage, buds, stems, and fruit of
infested plants may become red,
bronze, yellow, white or brown. Spider
mites spin webs.
Stippling or
mottling
symptom of
spider mite
feeding.