Once the spines of the whip spider get you, there is no escape.
The whips of the whip spider are its incredibly long front legs used to locate prey, mates, and danger.
Last week on a nighttime adventure in the rainforest, we a met the very cool headlight beetle illuminating its journey through the rainforest. But this was not the only encounter with a spooky denizen of the dark. Resting on the trunk of a tree was a really mysterious arachnid called the whip spider, a.k.a. tailless whip scorpion. While not really a scorpion or a spider, this bizarre creature is a member of an arachnid clan known as Amblypygi. Whereas spiders and true scorpions amble about on four pairs of legs, whip spiders use just three pairs for nocturnal strolls. The fourth pair of legs, found at the front of the creature, is extraordinarily long and thin and loaded with sensory structures to detect odors and objects including mates, offspring, and prey. These so called “whips” can be three to six times the length of the body and give the whip spider its common name. Whips can move in an almost complete circle around the creature and are very useful for detecting objects ahead, behind, above, and to the sides in a world of darkness.
A walk in the tropical rainforest at night is an awesome adventure filled with encounters with fearsome creatures. Resting on the trunk of a tree we discovered a whip spider just waiting for some hapless victim to stroll by. Super long front legs detect prey and wicked spines on the pedipalps guarantee there is no escape. A slight movement by the camera guy caused the whip spider to jet out of sight. Even slowed by 85%, the whip spider vanished almost too quickly to see.
Just in front of the whip-like legs is a pair of terrifying hinged appendages known as pedipalps. This “sit and wait” predator uses its pedipalps to capture prey in much the same fashion as a praying mantis uses its spiny forelegs to grab its victims. As a tasty morsel enters range, a rapid strike of the pedipalps ensnares the prey in comb-like spines. Usual meals include crickets, cockroaches, spiders and moths, but small lizards and even fish are known to be eaten by these clever predators. Once captured, the victim is pulverized by two grinding jaws called chelicerae. Digestive enzymes added to the pulpy mass enable the whip spider to ingest the liquefied meal.
Who knows what the leaflike expansions are for on the hind legs of this tiny whip spider?
As frightening as whip spiders appear, they are truly harmless to humans. In fact, some species have several admirable and somewhat endearing behaviors. One such behavior is a fine sense of direction. While wandering about the rainforest at night it is easy to get lost. On more than one occasion, hapless adventurers have disappeared into a ravine while searching for a trail in dense tropical vegetation. Not so the whip spider! Research has shown that some whip spiders can find their way home after being moved more than 30 feet away from their refuge, all of this without Google Maps.
For any mothers who might be reading this episode, think about the calories you burned lugging youngsters about when they wanted to be picked-up. Whip spiders lay from 10 to 90 eggs at a time. Mother whip spiders typically carry their young on their backs for several weeks after offspring hatch from eggs. In captivity, females of the Floridian whip spider, Phrynus marginemaculatus, continue to interact with their offspring for several months after the babes have departed from their mother’s back. Mothers were observed to move between small clusters of young ones. Females and offspring frequently engaged in gentle mutual stroking with their whip-like legs. How often these fascinating behaviors happen in the wild remains to be seen. The message conveyed by the mutual stroking is known only to the whip spider and her young, but on a dark night in the rainforest a gentle touch from mom could be a comforting signal, even to a whip scorpion.
Watch as the whip spider senses the approaching danger of a giant finger and rockets out of harm’s way. At one tenth of normal speed, see how the whip-leg of the arachnid reaches back to examine the intruder’s finger before turning on the speed to escape.
References
On the steps of El Castello at the Mayan ruin of Xunantunich, students discover Mayan history and look forward to nighttime adventures in a tropical rainforest where amazing insects and arachnids abound.
Bug of the Week gives special thanks to Drs. Dan Gruner and Paula Shrewsbury, the hearty crew of BSCI 339M: Tropical Biology and Maya Culture, and the fearless guides at the Toucan Ridge Ecology and Education Center and Cockscomb Wildlife Sanctuary who were the inspiration for this episode. Kenneth J. Chapin and Eileen A. Hebets’ treatise, “The behavioral ecology of amblypygids”, and the wonderful article “Social behavior in Amblypygids, and a reassessment of arachnid social patterns” by Linda Rayor and Lisa Anne Taylor, were used as references for this episode.
