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