ArthropodArthropods (ˈɑːrθrəpɒd, (gen. ποδός)) are invertebrate animals in the phylum Arthropoda. They possess an exoskeleton with a cuticle made of chitin, often mineralised with calcium carbonate, a segmented body, and paired jointed appendages. In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one. They are an extremely diverse group, with up to 10 million species. Haemolymph is the analogue of blood for arthropods.
SpiderSpiders (order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species diversity among all orders of organisms. Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every land habitat. , 50,356 spider species in 132 families have been recorded by taxonomists.
ArachnidArachnida (əˈræknɪdə) is a class of joint-legged invertebrate animals (arthropods), in the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaroons. Adult arachnids have eight legs attached to the cephalothorax, although the frontmost pair of legs in some species has converted to a sensory function, while in other species, different appendages can grow large enough to take on the appearance of extra pairs of legs.
ChelicerataThe subphylum Chelicerata (from Neo-Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mites, among many others), as well as a number of extinct lineages, such as the eurypterids (sea scorpions) and chasmataspidids. The Chelicerata originated as marine animals in the Middle Cambrian period; the first confirmed chelicerate fossils, belonging to Sanctacaris, date from 508 million years ago.
InsectInsects (from Latin insectum) are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes and one pair of antennae. Their blood is not totally contained in vessels; some circulates in an open cavity known as the haemocoel. Insects are the most diverse group of animals; they include more than a million described species and represent more than half of all known living organisms.
CheliceraeThe chelicerae (kəˈlɪsəriː) are the mouthparts of the subphylum Chelicerata, an arthropod group that includes arachnids, horseshoe crabs, and sea spiders. Commonly referred to as "jaws", chelicerae may be shaped as either articulated fangs, or similarly to pincers. Some chelicerae, such as those found on nearly all spiders, are hollow and contain (or are connected to) venom glands, and are used to inject venom into prey or a perceived threat.
CentipedeCentipedes (from Neo-Latin centi-, "hundred", and Latin pes, pedis, "foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek χεῖλος, kheilos, lip, and Neo-Latin suffix -poda, "foot", describing the forcipules) of the subphylum Myriapoda, an arthropod group which includes millipedes and other multi-legged animals. Centipedes are elongated segmented (metameric) creatures with one pair of legs per body segment. All centipedes are venomous and can inflict painful bites, injecting their venom through pincer-like appendages known as forcipules.
PedipalpPedipalps (commonly shortened to palps or palpi) are the second pair of appendages of chelicerates – a group of arthropods including spiders, scorpions, horseshoe crabs, and sea spiders. The pedipalps are lateral to the chelicerae ("jaws") and anterior to the first pair of walking legs. Pedipalps are composed of six segments or articles: the coxa, the trochanter, the femur, the short patella, the tibia, and the tarsus.
Arthropod legThe arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: coxa (meaning hip, plural coxae), trochanter, femur (plural femora), tibia (plural tibiae), tarsus (plural tarsi), ischium (plural ischia), metatarsus, carpus, dactylus (meaning finger), patella (plural patellae). Homologies of leg segments between groups are difficult to prove and are the source of much argument.
PredationPredation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the host) and parasitoidism (which always does, eventually). It is distinct from scavenging on dead prey, though many predators also scavenge; it overlaps with herbivory, as seed predators and destructive frugivores are predators. Predators may actively search for or pursue prey or wait for it, often concealed.
