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the exterior protective or supporting structure or shell of many animals (especially invertebrates) including bony or horny parts such as nails or scales or hoofs


a tough semitransparent horny substance


a part that is joined to something larger

tracheal tube

one of many branching, air-filled tubes that extend throughout the bodies of many terrestrial arthropods


a breathing orifice

book lung

organ in many arachnids containing many thin folds of membrane resembling the leaves of a book

Malpighian tubule

saclike organ in most terrestrial arthropods that extracts wastes from the blood, adding them to feces that move through the gut


periodic shedding of the cuticle in arthropods or the outer skin in reptiles


region of a crustacean formed by the fusion of the head with the thorax


part of an insect's body that bears the wings and legs


the region of the body of a vertebrate between the thorax and the pelvis


hard outer covering or case of certain organisms such as arthropods and turtles


the lower jawbone in vertebrates


one of the first pair of legs of decapods


one of the paired abdominal appendages of certain aquatic crustaceans that function primarily for carrying the eggs in females and are usually adapted for swimming


either of the first pair of fang-like appendages near the mouth of an arachnid


pair of mouthparts in chelicerates that are usually modified to grab prey


organ in spiders that contains silk glands

incomplete metamorphosis

insect development consisting of three stages: egg, nymph, and adult


a larva of an insect with incomplete metamorphosis (as the dragonfly or mayfly)

complete metamorphosis

Insect development consisting of four stages: egg, larva, pupa, and adult


an insect in the inactive stage of development (when it is not feeding) intermediate between larva and adult


a chemical substance secreted externally by some animals (especially insects) that influences the physiology or behavior of other animals of the same species


an extended social group having a distinctive cultural and economic organization


a social class separated from others by distinctions of hereditary rank or profession or wealth


the internal skeleton

water vascular system

system of fluid-filled tubes used by echinoderms in locomotion and feeding and respiration

tube foot

tentacular tubular process of most echinoderms (starfish and sea urchins and holothurians) having a sucker at the end and used for e.g. locomotion and respiration


sievelike structure through which the water vascular system of an echinoderm opens to the outside

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