Množina: arachnids

Or arachnoid; Type of arthropod, including spiders, scorpions, and mites. They differ from insects in possessing only two main body regions, the cephalothorax and the abdomen, and in having eight legs.
Air-breathing arthropods characterized by simple eyes and four pairs of legs; SYN. arachnoid.
Creature of the natural class Arachnida, including spiders, mites, etc.
Any of a class (Arachnida) of arthropods comprising chiefly terrestrial invertebrates, including the spiders, scorpions, mites, and ticks, and having a segmented body divided into two regions of which the anterior bears four pairs of legs but no antennae

Množina: Arachnidans