The family Salticidae, commonly known as jumping spiders, is the largest family of spiders, encompassing over 6,000 described species worldwide. These arachnids are easily distinguished by their compact, often colorful bodies and a unique eye arrangement that gives them a distinct, almost flat-faced appearance. Unlike many of their relatives, jumping spiders are diurnal, using their agile movements to explore their environment. Their visual capabilities and characteristic jerky movements set them apart from the typical image of a spider waiting passively in a web.
Web Construction for Hunting
Jumping spiders do not construct the large, sticky, prey-snaring webs typical of species like orb-weavers. Their hunting strategy is based on active pursuit and ambush rather than passive trapping. They do not rely on ensnaring insects to secure a meal, and their silk is not engineered for capturing prey. This active hunting style is directly linked to their highly developed sensory organs and locomotive abilities.
The Silk Safety Tether
The primary use of silk for a jumping spider is a continuous strand called the dragline. This silk is anchored to the substrate before the spider moves or executes one of its powerful leaps. This line acts as a safety tether, ensuring that if a jump misses its target or the spider is dislodged, it can arrest its fall and haul itself back up. The dragline is also dynamically controlled during the jump. The spider can adjust the tension of the unwinding silk mid-air, which helps stabilize its body and control its pitch for an optimal landing posture.
Building Nests and Nurseries
Silk is utilized to build semi-permanent structures for shelter and reproduction. Jumping spiders create small, dense silken retreats, often called resting sacs or “pup tents,” in crevices or on leaves. These shelters provide protection from adverse weather, serve as a secure location for molting, and are used for nightly rest. Females also construct specialized silken nurseries or egg sacs to house and protect their eggs. The female will remain with the eggs, guarding them until the spiderlings emerge.
Vision-Based Predation
Jumping spiders do not need a sticky web because of their vision, which is among the best in the arthropod world. They possess eight eyes, with the two prominent anterior median eyes providing high-resolution, stereoscopic vision and accurate depth perception. This visual acuity allows them to spot and track prey up to 20 body lengths away. Hunting involves a calculated approach, where the spider stalks its target, determines the precise distance, and then uses a hydraulic burst of fluid pressure in its legs to propel itself onto the prey. This behavior, which includes planning detours to reach unseen prey, completely bypasses the need for a web trap.