The phrase “barking spider” refers to a large arachnid whose common name suggests an unusual ability. This name is not a literal description of a dog-like sound, but rather a recognition of the loud, startling noise the spider produces when threatened. This intriguing behavior and formidable appearance explain the origin of this memorable common name.
Identity and Classification
The barking spider is a large, hairy tarantula, primarily belonging to the Australian genera Selenocosmia and Phlogius (e.g., Selenocosmia stirlingi and Phlogius crassipes). It is a member of the Theraphosidae family, the true tarantulas, and is sometimes called a whistling spider or bird-eating spider. Females can reach a body length of up to 6 centimeters, with a leg span stretching to 16 centimeters.
These tarantulas are characterized by thick, powerful, hair-covered legs and a dark brown to black coloration. Like all spiders, they possess two main body segments—the cephalothorax and the abdomen—eight legs, and two palps used for sensing and manipulating prey. They are classified as Mygalomorphs, an ancient group of spiders built for digging, which contrasts with the more common Araneomorph spiders.
The Source of the “Bark”
The “bark” is not vocalized but is produced through stridulation, a defensive act common among various insects and arachnids. Stridulation occurs when the spider rapidly rubs two specialized, hardened body parts together to create friction. The sound is generated by rubbing rows of modified spines on the basal segments of their palps against opposing spines found on their chelicerae (jaw bases).
This scraping action creates a distinct, audible hissing or humming sound that serves as a warning to potential predators. The noise is most readily produced when the tarantula adopts a threatening, defensive posture, rearing up to display its fangs. This acoustic defense deters animals like owls, dingoes, or goannas before a physical confrontation is necessary.
Habitat, Behavior, and Danger
The Australian barking spiders inhabit arid and semi-arid regions, leading a largely fossorial (burrowing) existence. They construct deep burrows in sandy or loamy soil, which helps maintain the stable, humid environment necessary for their gill-like lungs. These tarantulas are nocturnal ambush predators, spending their days hidden underground and emerging at night to hunt from the entrance of their silk-lined burrows.
Their diet consists mainly of insects, frogs, and small lizards, which they quickly grasp and subdue with their venom. The venom is potent to small animals but is generally not considered medically significant or dangerous to adult humans. A bite can be painful and may cause localized swelling, though the spider typically only bites if severely provoked. Unlike some New World tarantulas, the Australian barking spider does not possess urticating hairs, relying instead on its size, aggressive defensive display, and the startling effect of stridulation.