Tap to explore
Anatomy
Ranging across the world, in tropical and subtropical regions, the Whip Spider (Amblypygi) is uniquely alien in appearance. Although their fearsome looks may inspire fear they are quite harmless to humans. And although closely related to spiders they are in fact very different. Whip Spiders do not spin webs or even possess silk glands. Nor do they use fangs to inject venom into prey.
Tap to explore
Feelers
The modified front legs used as feelers are the Whip Spider's main sense receptors and allow them to feel threats or prey in an area many times the width of their body. They will often use each independently to feel the surrounding terrain, and are invaluable in assisting the nocturnal Whip Spider as it hunts in the dark.
Tap to explore
Eyes
Like most arachnids, Whip Spiders have 8 eyes; 2 in front, and 3 to each side. But even with 8 eyes Whip Spiders have poor vision and depend on their specialized feelers to navigate their surroundings.
Tap to explore
Legs
Unlike spiders with 8 legs used for walking, Whip Spiders only use 6. The front pair are instead used as feelers. It is from the appearance of these long, thin, specialized legs that they get the name Whip Spider.
Tap to explore
Grabbing arms
The prominent pair of grabbing arms up front are actually modified pedipalps. Pedipalps are used as sense organs on most other arachnids, but on the Whip Spider they have developed into predatory claws used for capturing prey. Each arm is lined with sharp spines that help hold and drag prey closer to the Whip Spider's mouth.
Tap to explore
Mating Habits
Whip Spiders are semi-social so it's not uncommon for them to live in small groups usually consisting of a single male with several females. This is another trait that differentiates them from most other arachnids. Males tend to be territorial and will fight for dominance, which is why we will generally find only one mature male within a group.
Tap to explore
Eggs
Once fertilized the female will drop her eggs into a sack carried beneath her abdomen. This keeps them hidden while they develop.
Tap to explore
Sexual Dimorphism
Like many other animals Whip Spiders show physical differences between the sexes, though in this case the differences are subtle. The most obvious being that the joint in the male Whip Spider's grabbing arms, the elbow, extends past the first joint in the legs, while in females these joints are usually aligned.
Tap to explore
Mating
When seeking a mate, males deposit a spermatophore, a stalk with a sperm mass on the tip, onto a nearby surface. He will then gesture with his arms to attract the attention of females. Once he finds a receptive female he uses his arms to guide her over the spermatophore, which is shaped to fit into a notch in the underside, thus depositing the sperm.
Tap to explore
Survival skills
Whip Spiders tend to blend in with their surroundings, but they have other ways to hide as well. Here we can see just how flat their body is. This makes them nearly invisible when seen from the side. It also allows them to retreat to safety and hunt in very narrow spaces. They are able to move with lightning speed, often side-ways like a crab, all the while remaining very flat.
Tap to explore
Keeping low
Keeping its body low also makes it nearly impossible to come between a Whip Spider and its footing. This makes capture very difficult.
Tap to explore
Standing tall
A Whip Spider can also raise its body up when necessary. We can see this one raising one side. They will sometimes stand tall and spread their spiked arms in order to appear as large as possible when confronted with a threat.
Tap to explore
Flat
In addition to the obvious advantages to keeping a low profile, remaining flat gives the Whip Spider a very secure grip. The wide-set legs create a stable platform from which to launch their grabbing arms at prey.
Tap to explore
Molting
Like all invertebrates Whip Spiders must molt in order to grow. Here we are lucky enough to see a female that has just pulled from her old exoskeleton. They look quite different in this soft, vulnerable state: now predominantly white rather than black, with green showing on the abdomen.
Tap to explore
As the new exoskeleton hardens it passes into deepening shades of green then blue before assuming the normal dark coloration. Whip Spiders are one of the few invertebrates that continue to molt even after reaching adulthood.
Tap to explore
Molt
Molting is a dangerous but necessary process in the life of all invertebrates. Since their skeletal system is on the outside of their body the only way to grow is to pull out of the old skeleton. Before this can happen they become very soft and vulnerable to damage. In this state they are unable to eat or even defend themselves.
Tap to explore
Growth
When the Whip Spider has fully exited, the new body expands to a size noticeably larger than before. It will take several days before this new exoskeleton has fully hardened. Over this time the Whip Spider will remain hidden in a safe place.
Tap to explore
Escape Hatch
Once the body becomes soft and pliable, the Whip Spider pushes out of the back of its carapace, which pops open allowing it to slowly squeeze out. Hanging upside-down to allow gravity to assist the process, it will meticulously work each limb out of the old shell. The length of the feelers requires it use the grabbing claws to gently pull them out.
Tap to explore
The Nymphs
After 3 to 5 months the egg sac cracks open and the nymphs crawl onto their mother's back. They will remain there until their first molt, at which time they will leave their mother and venture into the world on their own.
Tap to explore
Within days they will need to find prey and eat their first meal. They will assume the normal coloration of a Whip Spider after the following molt. Until then they retain some of the green body color and reddish arms.
Tap to explore
Piggy back
The mother will carry her nymphs, guarding against danger. We see this in certain other arachnids as well. This is to protect the vulnerable nymphs until they can fend for themselves.
Tap to explore
First Molt
After approximately 10 days the young will begin to molt, a few at a time, leaving the mother's back as they do so. When all are done the mother is left with a ball of intertwining shed skins still clinging to her back.
Tap to explore
Social connection
Without their mother watching over them the nymphs will not survive. This is partially due to the social interaction between mother and nymphs. There is additional interaction among the nymphs that helps them to feel safe.