By: Anna Grace Watkins

Arthropod Characteristics: Arthropods pollinate many of the flowering plants on Earth. Arthropods are bilateral symmetrical. They have an exoskeleton and appendages. An appendage is any structure, such as a leg or an antenna, that grows out of the body of an animal. They help the arthropod with its sensing, walking, feeding, and mating. Some arthropods have a head and a fused thorax and abdomen, but others have an abdomen and a fused head and thorax called a cephalothorax.

Characteristics Continued: Arthropods must shed their old exoskeleton often. They are very successful due to the presence of an exoskeleton. This process is called molting. They go through this because their exoskeleton can not grow, but before it molts, a new, soft exoskeleton is formed from chitin-secreting cells beneath the old one. But while the new exoskeleton is soft,they become very venerable to predators because they can not protect their selves. Most arthropods molt four to seven times in their lives.

Characteristics Continued: Most arthropods are segmented, but not as much as worms. There are 3 sections: Head Thorax Abdomen

Characteristics Continued: Arthropods are mostly very quick! They crawl, run, climb, dig, swim, and fly. They have an open circulatory system with vessels that carry blood away from their hearts. Also has a complete digestive system with a mouth, stomach, intestine, and anus. Arthropods also reproduce sexually. They have a wide variety of respiratory structure. Gills, book lungs, & tracheal tubes! Other openings in their body is spiracles.

Characteristics Continued: Arthropods have acute senses. Some can even communicate by pheromones, which are chemical odor signals given off by animals. Their vision is also very important also. Most have a pair of large compound eyes and from three to eight simple eyes. Compound eyes can detect movements of prey, mates, or predators, and can also detect colors. Arthropods also have well-developed nervous system that process information coming in from the sense organs. Its simple nervous system consists of a double ventral nerve cord, an anterior brain, and several ganglia. The ganglia acts as control centers for the body section in which they are located.

Class Arachnida: 30,000 Species! But only a dozen a harmful to humans. Spiders are the largest group of arachnids. Arachnids have 6 pairs of jointed appendages. The first pair of appendages are called chelicerae. (pinchers/fangs) The second pair of appendages are called the pedipalps. The remaining 4 appendages are modified as legs for locomotion. No antennae! Has structures called spinnerets where the spider silk is secreted and is spun into thread. 2 body regions. The Cephalorthorax The Abdomen

Class Arachnida Pictures: Spider: Scorpion:

Class Diplopoda: Millipedes eat mostly plants and dead material on damp forest floor. They do not bite, but can spray bad smelling fluids from their defensive stink glands. There are estimated 8,000 species. Centipedes are found in an array of terrestrial habitats from tropical rainforests to deserts. they are found in soil and leaf litter, under stones and deadwood, and inside logs.

Millipede Pictures:

Class Crustacea: Crustaceans are aquatic. They exchange gas as water flows over feathery gills. They are the only arthropods that have two pairs of antennae for sensing. Some have 3 body sections & others only have 2. Many have five pairs of walking legs that are used for: Walking Seizing prey & cleaning other appendages All have: Mandibles for crushing food. 2 compound eyes.

Class Crustacea Pictures: Lobster! Crab!

Class Chilopoda: Centipedes are carnivorous and eat soil arthropods, snails, slugs, and worms. When they bite you its very painful to humans. They have Malpighian tubules for excreting waste. Millipedes have tracheal tubes! They may have from 15 to 181 body segments. But they always have an odd number of segments.

Centipede Pictures:

Class Merostomata: It includes only four living species. These arthropods migrate to shallow water during mating season. Female lay their eggs on land, buried in sand above the high water mark. They possess compound eyes. Also have a semicircular exoskeleton, and a long pointed tail. They also have 4 pairs of walking legs. 5 or 6 pairs of appendages that movie over their gills.

Class Merostomata Pictures:

Class Insecta: Class Insecta is by far the largest group of arthropods. Insects mate more than once, or less during their lifetimes. The eggs are fertilizes internally and in some species, shells form around them. Most lay a large number of eggs. Females are equipped with an appendage that allows the insect to pierce through the ground or wood service to lay its eggs in the hole. Some insects go through complete metamorphosis, where the insect goes through a series of developmental changes from egg to nymph. Egg Larvae Pupa Adult Others go through incomplete metamorphosis, where the insect goes through only three stages of development. Egg Nymph Adult

Class Insecta Pictures: Butterfly Grasshopper