Amblypygi (Whip Spider)

Amblypygi is an order of invertebrate animals belonging to the class Arachnida, in the subphylum Chelicerata of the phylum Arthropoda. They form a separate order of arachnids alongside the spiders, scorpions, and others.

Amblypygids are also known as whip spiders and tailless whip scorpions (not to be confused with whip scorpions that belong to the Arachnid order Thelyphonida.) The name "amblypygid" means "blunt rump", a reference to a lack of the flagellum ("tail"). They are harmless to humans. Amblypygids possess no silk glands or venomous fangs. They rarely bite if threatened, but can grab fingers with pedipalps, resulting in thorn-like puncture injury.

By 2003, 5 families, 17 genera and around 155 species had been discovered. They are found in tropical and subtropical regions worldwide. Some species are subterranean; all are nocturnal. Fossilized amblypygids have been found dating back to the Carboniferous period, for example Graeophonus.

Anatomy
Amblypygids range from 3 to 23.6 inches (7.6 to 60 cm) in size according to legspan.[5] Their bodies are broad and highly flattened, with a solid carapace and a segmented abdomen. They have a pair of median eyes at the front of the carapace, located just above the chelicerae (in a manner somewhat similar to that of crustaceans), and possessed three smaller eye pairs placed further back on each side, for a total of eight eyes.

Amblypygids possess medium to poor eyesight. Their pedipalps, which serve as sensors for many related arachnids, are modified for grabbing and retaining prey, much like those of a mantis. 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 body. Typically, the animal holds one of these legs out in front of it as it moves, and uses the other to probe the terrain to the side.

Behavior
Amblypygids often move about sideways on their six walking legs, with one "whip" pointed in the direction of travel while the other probes their other sides. Prey are located with these "whips", captured with pedipalps, then masticated with chelicerae.

Comparing the front and back legs of an Amblypygid

Courting rituals involve the male depositing stalked spermatophores, which have one or more sperm masses at the tip, onto the ground, and using his pedipalps to guide the female over them. She gathers the sperm and lays fertilized eggs into a sac carried under theabdomen. When the young hatch, they climb up onto the mother's back; any which fall off before their first moult will not survive.

Some species of Amblypygi, particularly Phrynus marginemaculatus and Damon diadema, may be among the few examples of arachnids that exhibit social behavior. Research conducted at Cornell University suggests that mother amblypygids communicate with their young with her anteniform front leg, and the offspring reciprocate both with their mother and siblings. Further, the whip spiders would seek each other out and gather into a group when placed in an unfamiliar environment.

Amblypygids will consume any appropriately sized prey. Most of their diet likely consists of insects. Like many opportunistic predators, amblypygids can survive for two or three weeks without food. Before, during and after molting they generally do not feed. Like any other arachnid, an amblypygid will molt several times during its life.

Genera
The following genera are recognised:
 * Palaeoamblypygi  Weygoldt, 1996
 * Paracharontidae  Weygoldt, 1996
 * Paracharon  Hansen, 1921  (1 species)
 * Euamblpygi  Weygoldt, 1996
 * Charinidae  Weygoldt, 1996
 * Catageus  Thorell, 1889  (1 species)
 * Charinus  Simon, 1892  (33 species)
 * Sarax  Simon, 1892  (10 species)
 * Neoamblpygi  Weygoldt, 1996
 * Charontidae  Simon, 1892
 * Charon  Karsch, 1879  (5 species)
 * Stygophrynus  Kraepelin, 1895  (7 species)
 * Unidistitarsata  Engel & Grimaldi, 2014


 * Phrynoidea  Blanchard, 1852
 * Phrynichidae  Simon, 1900
 * Damon  C. L. Koch, 1850  (10 species)
 * Euphrynichus  Weygoldt, 1995  (2 species)
 * Musicodamon  Fage, 1939  (1 species)
 * Phrynichodamon  Weygoldt, 1996  (1 species)
 * Phrynichus  Karsch, 1879  (16 species)
 * Trichodamon  Mello-Leitão, 1935  (2 species)
 * Xerophrynus  Weygoldt, 1996  (1 species)
 * Phrynidae  Blanchard, 1852
 * Acanthophrynus  Kraepelin, 1899  (1 species)
 * †Britopygus  Dunlop & Martill, 2002  (1 species; Cretaceous)
 * †Electrophrynus  Petrunkevich, 1971  (1 species; Miocene)
 * Heterophrynus  Pocock, 1894  (14 species)
 * Paraphrynus  Moreno, 1940  (18 species)
 * Phrynus  Lamarck, 1801  (28 species, Oligocene - Recent)