Tarantulas comprise a group of large spiders of the family Theraphosidae. Although slow and deliberate, these arachnids are known for being accomplished hunters, preying mainly on insects and other bigger game.
Aside from their weight and body length, another characteristic that sets tarantulas apart from other spiders is their "furry" bodies. So why do these animals look so hairy?
Unusual Body Covering
A female tarantula has a more stocky body and is covered in light brown or tan hair. Meanwhile, the male tarantula is thinner and lankier, with black hair covering most of its body and reddish hairs on its abdominal area.
Unlike mammal hair, which is made of keratin, the hair that covers tarantulas, known as setae, is made of chitin. This organic polymer is a derivative of glucose that also makes up the structure of a spider's exoskeleton. These hairy coverings are mainly found on the legs and mouthparts of the spiders. They feed into sensory nerves found in the tarantula's skin or cuticle.
Sensing the World
The hairs that cover the body of tarantulas are more important than you might think. Unlike human hairs, which have very limited functions, hairs on tarantulas can do a lot of things, according to Jerome Rovner from the Journal of Arachnology.
Tarantulas are covered with hair for various reasons. Some of these setae act as sensory organs that help tarantulas taste, smell, touch, and detect vibrations from their surroundings. The most sensitive hairs are trichobothria, the covering that can detect even the smallest changes in air movement. This sensitivity is made possible by the ball and socket attached to the membrane in the cuticle.
These hairs also serve as a tarantula's guide in capturing or responding to escaping prey. German zoologist Friedrich Dahl named these hearing hairs in 1883 when he noticed that they moved to the sound of a violin.
The chemically sensitive hairs used for smelling and tasting are hollow and blunt. They also play a vital role in reproduction and help the arachnid look for a potential mate. Male tarantulas wander in search of a female's burrow. If they walk near such a burrow, their contact chemosensitive hairs get stimulated by the pheromone, which is bound to silk lines near the burrow's entrance. This enables the male to find the female. Rovner added that these hairs could also detect chemicals left by nearby prey.
Aside from sensing and reproduction, tarantulas' hairs have three other functions. First, they help the cold-blooded arachnids regulate their body temperature. The hairs trap a layer of air against their body and appendage cuticle, creating insulation. With a thick coat of these hairs, tarantulas can remain active throughout cold nights in deserts and tropical rainforests.
Additionally, the long hair functions as a waterproof coat that repels water if the spider gets submerged by flooding. Finally, the undersurface of tarantulas' leg hairs is sticky for a significant reason. They help the tarantulas climb smooth vertical surfaces. They also contain dense networks of bristles called scopulae, which help them capture prey.
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