Many people wonder about the relationship between jumping spiders and tarantulas, often questioning if one is a type of the other. Understanding their differences and shared characteristics clarifies their unique places within the diverse world of spiders.
The World of Jumping Spiders
Jumping spiders are a diverse family of spiders, known scientifically as Salticidae, encompassing over 600 genera and 6,000 species. These spiders are generally small, with body lengths typically ranging from a few millimeters up to about 1.5 centimeters. They often display vibrant colors and iridescent patterns. A defining feature of jumping spiders is their large, forward-facing principal eyes, which provide exceptional vision.
Their name directly reflects their primary mode of locomotion and hunting: a distinctive jump powered by a sudden increase in hydraulic pressure in their legs. Unlike many other spiders, jumping spiders do not typically spin large webs to capture prey. Instead, they are active diurnal hunters, stalking their insect prey with precision before pouncing. These intelligent hunters use their acute vision to locate and track targets, often performing complex maneuvers to ambush unsuspecting insects. Jumping spiders are not considered dangerous to humans; their bites are rare and usually result in only minor, localized irritation, similar to a bee sting.
The World of Tarantulas
Tarantulas belong to the family Theraphosidae, a group of large, often hairy spiders. These spiders vary significantly in size, with leg spans ranging from a few centimeters to nearly 30 centimeters in some species. Their robust bodies are typically covered in dense hair, which can serve various functions, including sensory perception and defense. Tarantulas generally have smaller eyes compared to jumping spiders, and their vision is not as acute, relying more on vibrations and touch to navigate and detect prey.
Many tarantula species are ambush predators, spending much of their time in burrows or natural crevices, waiting for prey to pass by. They are less active hunters than jumping spiders, often emerging at dusk or night to lie in wait for insects, small rodents, or lizards. While some species can be defensive, tarantulas are generally docile and non-aggressive towards humans. Some New World tarantulas possess urticating hairs on their abdomens, which they can kick off as a defense mechanism, causing irritation to skin or eyes. Their venom, while potent enough to subdue prey, is typically not medically significant to humans, although bites can be painful.
Distinguishing Features and Shared Traits
Jumping spiders and tarantulas exhibit several clear distinctions in their physical characteristics and behaviors. Jumping spiders are small, active hunters with exceptional vision and a unique hydraulic jump, rarely using webs. In contrast, tarantulas are larger, hairy ambush predators with less acute vision, relying on touch and vibrations.
Despite these observable differences, jumping spiders and tarantulas share fundamental characteristics as members of the order Araneae. Both are arachnids with eight legs, two main body segments (cephalothorax and abdomen), and chelicerae, which are mouthparts containing fangs used to inject venom into prey. Both groups also possess venom, though its potency and effects vary widely between species, and it is generally not life-threatening to humans. They are both carnivorous predators, playing roles in controlling insect populations within their respective ecosystems.
Evolutionary Paths of Spiders
The scientific classification of spiders provides a clear answer as to why jumping spiders and tarantulas are distinct, despite both being spiders. All spiders belong to the order Araneae, but this order is further divided into suborders, reflecting deep evolutionary divergences. Tarantulas are classified within the suborder Mygalomorphae, which represents an older lineage of spiders. These spiders are characterized by fangs that point downwards and parallel to each other, orthognathous chelicerae. Many mygalomorphs, including tarantulas, also possess two pairs of book lungs for respiration.
Jumping spiders, on the other hand, belong to the suborder Araneomorphae, which is a more recently evolved and diverse group. Spiders in this suborder, often called “true spiders,” have fangs that cross in a pincer-like action, labidognathous chelicerae. Most araneomorphs have one pair of book lungs, along with a tracheal system for breathing. This fundamental difference in fang orientation and respiratory structures reflects their separate evolutionary paths, meaning jumping spiders are not a type of tarantula, but rather distant cousins within the broader spider family tree.