Jumping spiders, members of the family Salticidae, are known for their active hunting style, relying on movement and vision rather than webs to capture prey. Ants are a common, though challenging, item on the menu for many species of jumping spiders. This predatory act is complex because ants possess strong defenses, yet the spiders’ unique adaptations allow them to overcome these dangers. While many jumping spiders are generalist predators, some have specialized their hunting strategies around eating ants.
The Defenses of Ant Prey
Ants defend themselves using a three-pronged strategy: chemical, physical, and social. Many ant species employ chemical defenses, using stings or spraying acidic compounds like formic acid, which can injure or kill a smaller attacker. Their exoskeletons also provide physical protection, with some species having large mandibles or specialized soldier castes.
The collective defense mechanism of the colony is a major threat. When a single ant detects danger, it releases alarm pheromones, recruiting nestmates to swarm the intruder. This coordinated group attack, often involving biting and stinging by dozens of individuals, makes a solo ant a dangerous target, as the spider risks being overwhelmed.
Jumping Spiders’ Predatory Advantage
Jumping spiders successfully navigate the dangers of ant predation using specialized adaptations. Their acute vision allows them to precisely calculate the distance and trajectory for a lethal attack. The large, forward-facing principal eyes provide high-resolution, three-dimensional vision, which is necessary for accurately judging the range to their target, a feature unique among invertebrates.
Visual acuity enables a precise hunting sequence. The spider first orients its body to focus its principal eyes on the ant, then begins a slow, deliberate stalk, often moving along a circuitous path. This patient approach minimizes the chance of alerting the ant, preventing the release of alarm pheromones that would trigger a swarm response.
Just before the final pounce, the jumping spider anchors a silk thread, known as a dragline, to the substrate. This silk tether serves as a safety line, providing both stability for the jump and a rapid escape route should the attack fail or if the spider is suddenly threatened. The spider then uses an internal hydraulic system to propel itself onto the ant with speed and accuracy, delivering a venomous bite that quickly paralyzes the prey.
Specialized Ant-Eating Spiders
While many jumping spiders consume ants opportunistically, some species specialize in ant-eating. These specialists have developed behavioral strategies to deal with the hazards of their prey. For example, some species in the genus Plexippus visually discriminate between different ant species, choosing to attack less aggressive or less chemically defended ones.
Another specialization is ant-mimicry, where the spider evolves to physically resemble an ant. This camouflage helps the spider avoid detection by ant predators that may avoid ants, or allows the spider to blend into ant columns to pick off vulnerable individuals. Even species without mimicry exploit ant-related resources; the Central American species Bagheera kiplingi, for instance, is primarily herbivorous, feeding on plant structures called Beltian bodies that are guarded by aggressive ants, occasionally stealing ant larvae as a protein supplement. These specialized species demonstrate that ants represent a valuable and consistent food source that has driven evolutionary adaptations in the jumping spider family.