Phylum Arthropoda

Phylum Arthropoda By Kayla Wilkinson

Class Arachnida • 30,000 species • Includes spiders, scorpions, mites, and ticks • Spiders are the largest group • 2 body regions: cephalothorax and abdomen in most arachnid • 6 pairs of jointed appendages

Class Arachnida • First pair of appendages known as chelicerae • Located near the mouth • Often modified pincers or fangs • Pincers used to hold food and fangs inject prey with poison • Spiders have no mandibles

Class Arachnida • Second pair of appendages known as pedipalps • Adapted for handling food and for sensing • In male spiders modified for carrying sperm during reproduction • Four other appendages are modified legs used in locomotion • Arachnids have no antennae

Class Arachnida • Ticks and mites have one body section • Head, thorax, and abdomen are fused • Ticks feed on blood from reptiles, birds, and mammals • Capable of expanding up to 1 cm or more after a meal • Also spread diseases

Class Arachnida • Mites are so small they are often not seen • You can feel them bite though • Scorpions easily recognized by many abdominal body segments and enlarged pincers • Long tail with venomous stinger at tip • Use it to paralyze large prey • Habitat: warm dry climates • Eat insects and spiders

Class Crustacea • Many are aquatic and exchange gases as water flows over feathery gills • Only arthropods to have 2 pairs of antennae for sensing • All have mandibles for crushing food, and 2 compound eyes • Mandibles open and close from side-to-side • Many have 5 pairs of walking legs • First pair often modified into strong claws for defense

Class Crustacea • Include crabs, lobsters, shrimps, crayfishes, barnacles, water fleas, and pill bugs • Some have 3 body sections and others have 2 • Sow bugs and pill bugs are only land crustaceans • Found in moist habitats

Class Chilopoda • Centipedes • Many tiny jointed legs • Flatten bodies • Carnivorous, eat soil arthropods, snails, slugs, and worms • When bitten it’s painful to humans • Have Malpighian tubules for excretion • Tracheal tubes for gas exchange

Class Diplopoda • Millipedes • Eats mostly plants and dead material on damp forest floor • Do not bite but can spray obnoxious-smelling fluids from their defensive stink glands • Cylindrical body • Move slowly and graceful • Tracheal tubes for gas exchange • Malpighian tubules for excreting waste

Class Merostomata • Horseshoe crabs • Considered living fossils • Remained relatively unchanged since Cambrian period • Heavily protected by extensive exoskeleton • Live on sandy or muddy ocean bottoms for seaweed, worms, and mollusks

Class Merostomata • They migrate to shallow water during mating season • Females lay their eggs on land, buried in sand above the high water mark • Newly hatched horseshoe crabs look like trilobites

Class Insecta • Includes flies, grasshoppers, lice, butterflies, bees, beetles, and more • Largest group of arthropods • Insects mate once or only a few times during their lifetime • Eggs are fertilized internally. Some species shells form around them • Most lay large amounts of eggs

Class Insecta • Undergo metamorphosis which is a series of changes controlled by chemical substances in the animal • Complete metamorphosis has four stages: egg, larva, pupa, adult • Incomplete metamorphosis has three stages: egg, nymph, adult

Phylum Arthropoda