ARTHRPPODSChapter 24

What is Entomology?The study of insects (and their near relatives).

Review of Zoological NomenclatureTaxonomic Categories

Kingdom - AnimalaePhylum - Arthropoda

Class - InsectaOrder - Coleoptera

Family - ScarabaeidaeGenus - Popillia

Genus & speciesPopillia japonica Newman

Characteristics of the PhylumArthropoda

• Segmented bodies (e.g., head, thorax, abdomen).

• Paired appendages (e.g., legs, antennae) are jointed.

• Chitinous exoskeletion that must be shed.

• Bilateral symmetry.• The nervous system is dorsal (belly)

and the circulatory system is open and ventral (back).

24.1

Arthropod Exoskeletons• Joints are made

of stiff and flexible cuticle to allow movement.

• The exoskeleton is made of many layers of chitin.– hard material

that protects the body

– must be shed in order to grow

Arthropod Classification– Crustaceans—live in oceans,

freshwater streams, and on land– Chelicerates—specialized dagger-

like mouthparts– Insects—most live on

land, have six legs – Myriapods

—long bodies and many pairs of legs

Crustaceans (Marine Arthropods)

– two distinct body sections, cephalothorax and abdomen

–one pair of appendages per segment

– two pairs of antennae–exoskeleton–carapace

24.2

Crustacean Appendages• Crustacean appendages are

used for a variety of functions.– collecting and manipulating food– attracting females– Protection– claws, antennae, walking legs,

swimmerets, and mandibles.

Types of Crustaceans. – Decapods such as lobsters and

crabs have ten legs.

–Barnacles are sessile filter feeders wrapped in a hard shell.

– Isopods such as pill bugs have flattened bodies and seven pairs of legs.

Chelicerate Arthropod Characters:• Pincher-like mouthparts -

chelicerae • NO antennae• Two body regions, usually -

cephalothorax & abdomen• Four pairs of legs• Horseshoe crabs and

arachnids are only living groups

poison gland

spinnerets

fangs

24.3

Arachnids are the largest group of chelicerates. • There are three major groups of

chelicerates.–horseshoe crabs–sea spiders–arachnids

Arachnids -- Spiders• All spiders make silk and

produce venom.

Metamorphosis

CHANGE IN FORM FROM EGG TO ADULT

IncompleteINCOMPLETEMETAMORPHOUS

Insects change shape gradually!

CompleteMetamorphosis

Four stages that all look different

Insects with Complete Metamorphosis

• beetles• bees, ants, wasps• Flies• butterflies

EGG LARVA PUPA ADULT

Insects with Incomplete Metamorphosis

• fleas• grasshoppers &

crickets

EGG NYMPH ADULT

Wings NOT fully

developed