You’re not looking at an alien. This is Phrynus marginemaculatus, a species of amblypygid native to southern Florida, Cuba and the Bahamas. Amblypygids are a type of arachnid, with classic arachnid attributes: two body segments and four pairs of legs. Yet one unique aspect of their anatomy sets them apart from other arachnid orders: they only use three pairs of legs for walking. The fourth pair, known as antenniform legs, are elongated sensory legs that they use to interact with their environment.
The sensory capabilities of these specialized annteniform legs (or “whips”) have only recently been uncovered by scientists. Amblypygids will “sweep” their environment with their whips, using sensory hairs on the ends to explore their surroundings. The whips are nearly three times as long as their walking legs, giving them ample room to explore. In addition to physical touch, some of these sensory hairs are olfactory receptors, meaning they allow the amblypygid to smell. These olfactory receptors act as a homing device, allowing the amblypygid to literally smell its way home.
The bulky pedipalps and absurdly long whips may give the tailless whip scorpion a ferocious, alien-like visage, but they are in fact, excellent caregivers. The young will climb onto their mothers back and remain there until their first molt. Even after molting, the young may maintain a relationship with their mother and siblings for the first year of their life, using those alien-like whips to interact and communicate with their family. This type of complex behavior is still being studied by scientists, along with the many other sensory capabilities of amblypygids.