 Arthropods are one of the most diverse and successful animals of all time, it is the largest phylum of animals.  The phylum is named for: arthron means “joint” in Greek, and podos means ‘‘foot”.  This phylum includes animals such as insects, crabs, centipedes, crustaceans and spiders.

 Arthropods have a segmented body, a tough exoskeleton, and joined appendages.  They use complex organ systems,like a well- developed heart with an open circulatory system, nervous system, and groups of muscles.  Terrestrial arthropods breathe through tracheal tubes and book lungs, while aquatic breathe through featherlike gills.

 In excretion, most terrestrial arthropods dispose of nitrogenous wastes using Malpighian tubes, while aquatic have diffusion.  Terrestrial have internal fertilization, while aquatic have both internal or external.  When they outgrow their exoskeleton, arthropods undergo periods of molting.

 Arthropods include herbivores, carnivores, and omnivores.  There are arthropods bloodsuckers, filter feeders, detritivores, and parasites.  Arthropod mouthparts have evolved in ways that enable different especies to eat almost any food you can imagen.  Their mouth parts range from pincers or fangs to sickle-shaped jaws that can cut through the tissues of captured prey.

 Arthropods are classified based on the number and structure of their body segments and appendages particularly their mouthparts.  The three mayor groups are crustaceans, spiders and their relatives, and insects and their relatives.

 Animals in subphylum Crustacea are primarily aquatic.  Crustaceans typically have two pairs of antennae, two or three body sections, and chewing mouthparts called mandibles.  This subphylum includes organisms such as crabs, shrimps, lobsters, crayfishes, and barnacles.

Crayfish live under rocks and debris on the muddy bottom of freshwater lakes, streams and rivers. They are active at night and crawl along the mud feeding on aquatic vegetation, worms, insects, mollusks, and decayed organic matter.  Fast Facts Type: freshwater crustacean Diet: ( They help clean the water by scavenging on dead matter ) Size: 2 to 6 inches (5 to 15 centimeters) long

 Fast Facts Type: Invertebrate Diet: Omnivore Size: 5 in (12.7 cm) Group name: Streams Protection status: None Did you know? Red crabs can stop traffic, puncture tires, and wander through any open doors during their migration to the sea. Size relative to a tea cup: They scavenge on fallen leaves, seedlings, fruits, and flowers, recycling nutrients and helping to determine the spread and composition of native flora.

 Horseshoe crabs, spiders, ticks, and scorpions are members of subphylum Chelicerata.  Chelicerates have mouthparts called chelicerae and two body sections, and nearly all have four pairs of walking legs. Lack of antennae.  The bodies of chelicerates are divided into a cephalothorax and an abdomen.

 Fast Facts Type: Bug Diet: Carnivore Average life span in the wild: Up to 30 years Size: 4.75 in (12 cm) long; leg span, up to 11 in (28 cm) Weight: 1 to 3 oz (28 to 85 g) Size relative to a tea cup:

Horseshoe crabs are considered living fossils. The elegant, but simplistic design includes a basic, hard, curved exoskeleton (carapace) protecting an underbelly of soft tissue–characteristics that have permitted them to evade predation by a variety of species that have long gone extinct. Live primarily in and around shallow ocean waters on soft sandy or muddy bottoms. They are able to survive a year without food, and endure extreme temperatures, and dramatic changes in salinity levels. “Horseshoe crabs have gone basically unchanged for 360 million years. But can they survive human predation? ” - Jordan Schaul

 Fast Facts Type: Bug Diet: Carnivore Average life span in the wild: 3 to 8 years Size: Average, 2.5 in (6 cm); Largest, 8.3 in (21 cm) Did you know? Scientists aren't sure why, but scorpions are fluorescent under ultraviolet light. Size relative to a tea cup:

Ecological importance  Arthropods are of ecological importance because of their sheer numbers and extreme diversity. More than 874,000 living species of arthropods have been identified, making up more than 80 percent of all named species of animals. However, it is estimated that many more thousands of arthropods exist that have not yet been named. Most of these unnamed species are small beetles and other insects, and most of these occur in old-growth tropical rain forests—areas that have not yet been well explored.  Arthropods are both harmful and helpful to humans. A few species are transmitters of bacteria or viruses that cause diseases such as malaria, etc. Some arthropods are a nutritious source of food in many parts of the world, and insects play an important role in pollination (a process necessary for production in many plants).

Eventually they reach a leg-span of over 3 feet and a weight of 10 pounds. Coconut crabs live on island beaches throughout the Indian and South Pacific Oceans. They live in dirt burrows and rock crevices, and scavenge for fruits and nuts, including coconuts, thus deriving their popular name.