Insects & arachnids
Why do we care about insects & spiders?
Importance of Insects
• Biocontrol

i.e. Lady bugs, lacewings, many
parasitic wasps, preying mantis
• Pollinators
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Bees, wasps & flies
• Conservation
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Largest group of animals
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Most are not identified or
named.
Key characteristics
• Wings
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Zero, one or two pairs?
• Antennae
Shape of antenna
 Number of segments in antenna
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• Tarsi
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How many segments?
Wings: Wingless
Wings: one pair
Or two?
Antenna
Tarsi
ORDER: Collembola
Have a furcula on the fourth abdominal segment
(the “spring” in springtails).
Thysanura : Silverfish
Ephemeroptera:mayflies
Odonata:
Damselflies & Dragonflies
Cannot fold wings over back.
Dragonflies:wings held horizontally.
Damselflies:wings held vertically.
Phasmida:
walkingsticks and leaf insects
• Most North American species are wingless.
• Able to regenerate legs (unlike most insects).
• Mimic plant parts.
Orthoptera:
Grasshoppers, crickets & katydids
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Can be winged or wingless
Long antennae & ovipositor
Chewing mouthparts
Large jumping hind legs.
Mantodea: the Preying mantis
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Carnivorous
Freely movable head
Large, spiny front legs
Highly cannibalistic

Poor choice for pest control because of cannibalism
Blattaria: cockroaches
• The most agile of the insects
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Engineers use cockroaches as mobility models.
None are known vectors of disease
Wide-bodied insects
Winged and wingless forms
 Hissing roaches are wingless.
Termites
Isoptera: Termites
• Now believed to be specialized cockroaches.
• Only reproductives are winged (king and queen).
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They bite their wings off after mating.
• All workers are juveniles, soft bodied.
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Workers can mature if king or queen dies in the colony.
• All termites have an endosymbiote that allows
them to digest wood.

Is lost during molting process, so it must be fed to them
by another termite.
Dermaptera: earwigs
• Have large forcep-like cerci on abdomen
• Can be winged or wingless
• Do not crawl into ears & eat people’s brains
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In fact, they rarely bite at all.
Use cerci as a defensive mechanism.
Plecoptera: Stoneflies
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All are aquatic
Despite complete wing development, are poor fliers.
Many species do not feed as adults.
Males “drum” on stones and rocks to attract mates.
Psocoptera: bark lice
• Winged & wingless species.
• Are related to lice.

Most psocoptera are not parasitic, however.
• Look like flies, but has TWO pair of wings.
Hemiptera: true bugs
• Front wings are partly thickened &
leathery
• Hind wings are usually shorter than
front wings
• Sucking mouthparts
• Large order, many variations
 Some are wingless
Homoptera: Hoppers, cicadas & aphids
• Very large group with considerable variation.

Many, like aphids and hoppers, are crop pests.
• Only obvious difference between Hemiptera &
Homoptera is where the beak begins on the head.
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Hemiptera : below eyes.
Homoptera: above or level with eyes.
Thysanoptera: thrips
• Tiny insects that are found in flowers.
• Wings are always fringed, with fringes being
more prominent than the wings.
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The wings are long & thin.
• Sucking mouthparts.
Coleoptera: Beetles
• Front wings are shell-like or leathery.
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Second pair is membraneous.
• Chewing mouthparts.
• Some are aquatic.
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Diving beetles & water tigers.
• Often very colorful.
Siphonaptera: fleas
• Always wingless
• All are ectoparasites
• Are laterally flattened.
Diptera (true flies)
• All dipterans have only two wings
 Hind wings evolved into knobby balancing organs
(halteres).
• Sucking mouthparts, with much variation.
• Many species are disease vectors.
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Mosquitoes
• Some species resemble bees.
Lepidoptera:
butterflies, skippers & moths
• Coiled, sucking mouthparts.
• Wings have many scales.
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Some primitive moths look like other insects.
• Very large and diverse order.
• Many are colorful, particularly butterflies.
Hymenoptera:
Wasps, bees, ants & hornets
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Most have a constriction between thorax & abdomen.
Chewing mouthparts.
Many have a stinger (modified ovipositor).
Social hymenoptera have ADULT workers.
Other invertebrates to consider
• Arachnids
• Crustaceans
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Only one terrestrial crustacean
Sowbugs, pillbugs, roly poly.
• Diplopoda
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Millipedes
• Chilopoda
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Centipedes
Arachnids
• Spiders, mites, ticks, scorpions,
harvestmen (Opiliones), sun spiders
(Solifugae), pseudoscorpions
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Key characteristic: eight legs.
Spiders
• Eight legs, two body parts (cephalothorax,
abdomen).
Harvestmen (Opiliones)
• Eight legs, one body part.
Pseudoscorpion
• 8 legs, pedipalps pincer-like, minute insects
Crustacean
• 2 antennae, 7 pairs of legs
Yummy crustaceans
Diplopoda (millipedes)
• Long insects, many segments. Two pair of
legs per segment.
Chilopoda (centipedes)
• Long insects, many segments. One pair of
legs per segment. All have poison glands.
The experiment
• Design an experiment that will examine
arthropod preferences

Choose one of the following:
Visual: different colors
Taste: different sweetners
Olfactory: different scents
 Some scents will act as REPELLENTS
• Add the experimental to the water
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You will NOT need much sugar or essential oil.
Insects VERY sensitive to scents and
taste, much more than humans!
The experiment
• Take the treated and untreated water with
you.
• Dig a hole and place the coffee cans inside.
Be sure to pat the soil right to the edge of
the can so insects have a clear access.
• Pour the experimental or untreated water
into the coffee can.
• Mark your can so you know which is the
control and which are the experimentals.
The experiment
• Check the pit traps for insects every couple
of days.
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Place any arthropod you find in the pit traps in
vials of alcohol to preserve them.
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If you have a lot of insects, you can pour the
water from the pit trap into a mesh. Save the
water so you can put it back into the pit trap.