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Arachnids are arthropods in the class Arachnida (/ ə ˈ r æ k n ɪ d ə /) of the subphylum Chelicerata. Arachnida includes, among others, spiders , scorpions , ticks , mites , pseudoscorpions , harvestmen , camel spiders , whip spiders and vinegaroons .
The arthropods are a phylum of animals with jointed legs; they include the insects, arachnids such as spiders, myriapods, and crustaceans. [1] Insects play many roles in culture including their direct use as food, [2] in medicine, [3] for dyestuffs, [4] and in science, where the common fruit fly Drosophila melanogaster serves as a model organism for work in genetics and developmental biology.
The four major groups of arthropods – Chelicerata (sea spiders, horseshoe crabs and arachnids), Myriapoda (symphylans, pauropods, millipedes and centipedes), Pancrustacea (oligostracans, copepods, malacostracans, branchiopods, hexapods, etc.), and the extinct Trilobita – have heads formed of various combinations of segments, with appendages ...
Spiders are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms [ 1 ] which is reflected in their large diversity of behavior.
Like most arthropods, spiders lack balance and acceleration sensors and rely on their eyes to tell them which way is up. Arthropods' proprioceptors, sensors that report the force exerted by muscles and the degree of bending in the body and joints, are well-understood. On the other hand, little is known about what other internal sensors spiders ...
Horseshoe crabs are arthropods of the family Limulidae and the only surviving xiphosurans. Despite their name, they are not true crabs or even crustaceans; they are chelicerates, more closely related to arachnids like spiders, ticks, and scorpions. The body of a horseshoe crab is divided into three main parts: the cephalothorax, abdomen, and ...
Despite their name and brief resemblance, "sea spiders" are not spiders, nor even arachnids. While some literature around the 2000s suggests they may be a sister group to all other living arthropods, [8] [9] their traditional classification as a member of chelicerates alongside horseshoe crabs and arachnids has regained wide support in ...
Unlike the majority of arachnids, which are oviparous, hatching from eggs, scorpions seem to be universally viviparous, with live births. [97] They are unusual among terrestrial arthropods in the amount of care a female gives to her offspring. [98] The size of a brood varies by species, from 3 to over 100. [99]