Insect & Arachnid Anatomy

​

Intro to Arthropods

Outline

• Insects and their relatives

• How insects rule the world

• Insect anatomy and biology

​

Insects and their relatives

• Arthropods are numerous and diverse

– Insects (beetles, flies, moths, earwigs, aphids)

– Arachnids (spiders, ticks, mites, scorpions)

– Crustaceans (crayfish, crabs, lobsters, sowbugs)

– Centipedes, millipedes

• Exoskeleton is a hard outer shell

• Not arthropods: slugs, snails, earthworms

• ​Gastropods

Basic insect body plan

Head

Thorax

Abdomen

Basic insect body plan

Head

Thorax

Abdomen

Basic arachnid body plan

Cephalothorax

Abdomen

Basic arachnid body plan

Cephalothorax

Abdomen

Insects

• 3 body regions

• 1 pair of antennae

• 3 pair of legs

• 2 pair of wings

Arachnids

• 2 body regions

• No antennae

• 4 pair of legs

• No wings

Draw

Draw an Insect

Draw

Draw an Arachnid

Insects rule the world!

• There are more insects

than all other plants and
animals combined

• There are more than 1

million different species

• 1 out of every 5 animals

is a beetle!

• Small size
• Multigenerational
• Flight
• Metamorphosis
• Wide variety in food

choices

• Wide variety in habitat

resources

Why are insects so successful?

Insect metamorphosis

Complete metamorphosis:

egg, larva, pupa, adult

e.g., beetles, butterflies, flies

Incomplete metamorphosis:
egg, nymph, adult

e.g., grasshoppers, true bugs

Images from Cornell University, Http://nides.bc.ca/Assignments/Insects/Metamorphosis3.htm

Insects eat everything

• Carnivore, animal matter

• Herbivore, plant matter

• Omnivore, plant and animal matter

• Detrivore, organic matter

• Saprophore, decaying matter

Are these insects?

Multiple Choice

Is this an insect?

• Yes

• No

Multiple Choice

Is this an insect?

• Yes

• No

Multiple Choice

Is this an insect or an arachnid?

• Insect

• Arachnid

• Neither

Multiple Choice

Is this an insect or an arachnid?

• Insect

• Arachnid

• Neither

How to ID insects: wings

beetle

wasp

butterfly

fly

earwig

grasshopper

true bug

© Marlin E. Rice

© Marlin E. Rice

Chewing:
grasshoppers,
beetles,
praying mantis

Piercing-sucking:

mosquitoes, true bugs

Siphoning:

butterflies, moths

Sponging:
house fly

How to ID insects: mouthparts

Images on this page from R. Bessin, University of Kentucky

How to ID insects: antennae

freenaturepictures.com

How to ID insects: legs

walking

pollen-carrying

digging

swimming and grasping

L. Jesse
L. Jesse

© Marlin E. Rice

Grasping​

Jumping