Definition of arachnidCategorized under "General"
Definition as written by greeniethumb:
air-breathing arthropods characterized by simple eyes and four pairs of legs
Definition as written by palmbob:
primarily carnivorous, 8 legged invertebrates typified by the spider and the mite, but including numerous other arthropods in the subphyllum Chelicerata. From a gardeners point of view, the distinction can become important when trying to eradicate arthropod pests with certain pesticides, some which ONLY have activity against insect nervous systems and no effect on arachnids (eg. trying to eliminate spider mites (a type of arachnid) with the insecticide imidocloprid). Note: not all arachnids have 4 pairs of legs (some of the legs never develop, as in the case of many Eryophyid mites which may only have 2 pairs of legs, but they are still arachnids).
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