Harry Potter's spider

Piero Fariselli

In the book 'Goblet of fire' by JK Rawlings a poor spider has been used to show the unforgivable curses to the students. Actually, in the corresponding movie, the creature was not a true spiders but a digital version of an arthropod normally known as 'whip spiders' or 'tailless whip scorpions'. These arthropods do really exist in nature, even though they are really difficult to meet. Scientifically known as Amblypygi, they are not spiders, they do not produce silk nor have poison glands, but are spider kin. Like spiders, Amblypygi possess four legs, a pair of palps (which are leg-like appendages) and chelicerae (the jaws). The palps are modified in raptorial arms with a spiny basket shape for capturing prey. Young usually have reddish palps with banded legs, while adults are colored more uniformly.

Phrynus sp.

male

This stunning animals are quite large to be arthropods, reaching a body length of several centimeters (3 or more). Despite of the fact that they have a terrifying aspect they are completely harmless for the humans. Of course this is not true for other smaller animals which can easily become their preys. Among whip spiders typical dishes we can number crickets, moths, and sometimes small vertebrates like young lizards an frogs.

The name 'whip spiders' comes from the fact that their first pair of legs (whip-like) are very long and thin. Whip spiders are almost blind and have nocturnal habits, they are also frequent in proximity of caves. For this reason their first long legs, that carry a lot of receptors, are the most important sensorial organs of these animals and are used to scan the environment. Typically they walk keeping one of the leg ahead and the other around their body. Another interesting characteristic is the fact that they can move laterally in crab-like way. However, when they need are really fast. The first time I met one, I approached him (probably was a male) too close and in a eye-blink he suddenly disappeared a meter apart in a rock cracks.

Phrynus sp. walking

They mainly live in humid tropics and subtropics, so that for an European like me it is necessary to go abroad to find them, looking in cracks and crevices between rocks, under loose bark, logs, and litter. During the day, it is more difficult to meet them, since they hide themselves. But of course if you are not well trained or you are not helped by a local entomologist guide you may waste a lot of time looking in wrong places!

I was quite fortunate founding three of them during a night walk in the 'Parque Nacional del Este' in the Dominican Republic.

Whip spiders are generally solitary, however it has been reported that a single tree trunk may house many individuals in different hides. Males change its daily rest location more frequently than females. This is probably due to the fact that males move to find new mating opportunities.

Males are quite aggressive and often perform a ritualized 'dance' when they encounter other males and concomitantly there are no females around. However, when females are present the males duel with other males by using their palps and jaws together to combat, usually until one abandon or fall on the ground.

Phrynus body

The reproductive behavior is quite similar to that adopted by scorpions. The male deposits a spermatophore (a packet with the male sperm), guides the female over it during the mating courtship until she collects the packet. Living in a wonderful climate with a perennial spring, they also have a never-ending reproductive season.

The females carry their eggs (generally from twenty to forty) under their abdomen for several months, and again similarly to scorpions the newly hatched whip spiders are carried for other several days on the back of the mother's body. This until the first molt, when they leave their mother to start their own adventure.