Amblypygi is an order of arachnids also known as whip spiders or tailless whip scorpions, not to be confused with whip scorpions or vinegaroons that belong to the related order Thelyphonida. The name "amblypygid" means "blunt tail", a reference to a lack of the flagellum that is otherwise seen in whip scorpions. Amblypygids possess no silk glands or venom. They rarely bite if threatened, but can grab fingers with their pedipalps, resulting in thorn-like puncture injuries.
As of 2023, 5 families, 17 genera and around 260 species had been discovered and described.[2] They are found in tropical and subtropical regions worldwide; they are mainly found in warm and humid environments and like to stay protected and hidden within leaf litter, caves, or underneath bark. Some species are subterranean; all are nocturnal. Fossilized amblypygids have been found dating back to the Carboniferous period, such as Weygoldtina.[1]
Being arachnids, Amblypygi possess two body segments; the prosoma and the opisthosoma, (often referred to as the cephalothorax and abdomen), four pairs of legs, pedipalps, and chelicerae. Their bodies are broad and highly flattened, with a solid prosoma and a segmented opisthosoma.[4]
Amblypygids range from 5 to 16 centimetres (2.0 to 6.3 in) in legspan.[5][6] Most species have eight eyes; a pair of median eyes at the front of the carapace above the chelicerae and 2 smaller clusters of three eyes each further back on each side.
The first pair of legs act as sensory organs and are not used for walking. The sensory legs are very thin and elongate, have numerous sensory receptors, and can extend several times the length of the body.[5][4]
Amblypygids have raptorial pedipalps modified for grabbing and retaining prey, much like the forelegs of mantises.[7] The pedipalps are generally covered in spines, used for impaling and capturing prey. They are kept folded in front of the prosoma when not in use.[4] Recent work suggests that the pedipalps display sexual dimorphism in their size and shape.[8]