Tarantulas, large and often hairy spiders, have long captured human imagination and fear. These ancient arachnids, with fossil records dating back to the Triassic Period, have remained largely unchanged for millions of years. Despite their formidable appearance, much common perception is based on misunderstanding rather than fact. This article clarifies the universal characteristics, essential biological processes, and common misconceptions about all tarantulas.
The Core Identity: What Defines Every Tarantula?
All tarantulas are classified within the family Theraphosidae, part of the infraorder Mygalomorphae. This classification means they share specific anatomical features that distinguish them from other spiders. Unlike “modern” spiders (araneomorphs), tarantulas possess fangs that move parallel to each other and point downwards, rather than crossing like pincers.
A tarantula’s body consists of two main sections: the cephalothorax (or prosoma) and the abdomen (or opisthosoma). The cephalothorax is covered by a hard, shield-like plate called the carapace, and it is from this fused head and thorax region that their eight legs, two pedipalps, and chelicerae (mouthparts containing fangs) extend. All tarantulas have a chitinous exoskeleton, which provides structural support and protection. While most spiders have eight eyes, tarantulas generally have poor eyesight, relying more on vibrations and touch through specialized hairs covering their bodies.
Life’s Essentials: How All Tarantulas Thrive
Tarantulas are carnivorous predators, primarily consuming insects and other arthropods. Larger species may occasionally prey on small vertebrates such as lizards, frogs, or rodents. They are opportunistic hunters, typically ambushing their prey at night rather than catching them in elaborate webs. Once captured, the tarantula injects venom through its fangs to immobilize the prey, then secretes digestive enzymes to liquefy its insides before sucking up the fluid.
A fundamental biological process for all tarantulas is molting, where they shed their rigid exoskeleton to grow. This process is essential because their exoskeleton does not grow with them, necessitating periodic shedding to accommodate increased size. Young tarantulas molt more frequently, sometimes monthly, while adults may molt once or twice a year or less often. During molting, the tarantula is particularly vulnerable as its new exoskeleton is soft and requires time to harden.
All tarantulas produce silk, though not primarily for capturing prey in large webs like many other spider species. Instead, tarantulas use silk for various purposes, including lining their burrows for support and stability. Silk is also used to construct egg sacs, where the female protects her eggs, and some species weave urticating hairs into the sac for defense. Silk can also serve as a substrate for sensing vibrations of approaching prey or threats.
Beyond the Fear: Universal Truths About Tarantulas
Despite widespread apprehension, tarantula venom is generally not considered medically significant or life-threatening to humans. Its effects are typically comparable to a bee sting, causing localized pain, swelling, and redness at the bite site. Severe allergic reactions are rare, similar to reactions some individuals might have to bee stings.
Tarantulas are not inherently aggressive towards humans and typically only bite if provoked or threatened. Their primary defensive behaviors include displaying a threat posture, such as raising their front legs, or, for many New World species, flicking irritating urticating hairs from their abdomen. These hairs can cause skin irritation, rashes, or inflammation if they come into contact with skin or mucous membranes.
Tarantulas fulfill an important ecological role as predators. By consuming a wide range of insects and other arthropods, they help regulate populations, contributing to the balance of the food chain. They also serve as a food source for various animals, including larger lizards, snakes, birds, and wasps. Their presence therefore supports biodiversity and natural pest control within their habitats.