Arthropods ©2009 Susan Anderson

Characteristics of Arthropods Invertebrates Lack a backbone Exoskeleton Skeleton on the outside of the body Made of “chitin” Must “molt” Segmented Body Easiest to see in centipedes and millipedes Seen in tails of shrimp and lobsters See chart on page 348 Jointed Appendages Highly specialized tools Examples: antennae, legs, swimmerettes

Origin of Arthropods Have been around 540 million years First arose in the oceans Today they are almost everywhere Some live in fresh or salt water Most, however do not live in saltwater, but almost everywhere else.

Crustaceans Have two or three body sections Usually have three pairs of appendages for chewing Five or more pairs of legs Two pairs of antennae Develop by metamorphosis Usually have gills Live in fresh and salt water and on damp land areas Feed as predators, carnivores, and herbivores

Arachnids Spiders, mites, and ticks Two body sections Cephalothorax Abdomen Four pairs of legs Book lungs Catch prey in many different ways Hollow fangs Mites On land, freshwater, saltwater May cause allergies Ticks Scorpions

Centipedes and Millipedes Highly segmented bodies Centipedes have one pair of legs per segment and are carnivores Inject a poison into their prey Millipedes have two pair of legs per segment and are herbivores Have an awful smelling liquid that they squirt when scared

Insects Three pairs of legs One pair of antennae Body divided into three segments Head, Thorax, Abdomen Many have wings Only invertebrates that can fly Metamorphosis Complete and Incomplete (Gradual)

Metamorphosis Complete Four stages Egg, Larva, Pupa,Adult Found in Butterflies, Moths, Fireflies Incomplete Three stages Egg, Nymph, Adult Found in Grasshoppers, Termites, Dragonflies

Ways Insects can be Beneficial Insects pollinate crops Make products like silk and honey Prey on pests

Arthropods