The relationship between insects and spiders is often viewed as the spider being the predator, and the insect the prey. This dynamic, however, is frequently reversed in the natural world. Certain insect groups have evolved highly specialized predatory strategies that target spiders. These insects range from generalist hunters that consume spiders for immediate nutrition to highly specialized wasps that employ complex biological mechanisms to ensure their offspring have a fresh meal.
Specialized Hunters: The Spider Wasps
The most famous insect predators of spiders belong to the family Pompilidae, commonly known as spider wasps. These solitary insects are characterized by their long, spiny legs and rapidly flicking their wings as they search for prey on the ground or vegetation. Spider wasps are specialized hunters that focus nearly exclusively on spiders, including large species like wolf spiders, huntsman spiders, and tarantulas.
A notable example is the Tarantula Hawk, a species of spider wasp that targets tarantulas many times its size. The female wasp locates a tarantula’s burrow and initiates a confrontation, using its mobility to avoid the spider’s defensive strikes. Once an opportunity arises, the wasp delivers a precise, powerful sting to the spider’s underside. This venom acts with speed and accuracy, paralyzing the spider almost instantly, allowing the wasp to drag the immobilized catch to a prepared nest site.
Generalist Insect Predators of Spiders
Not all insects that kill spiders are specialized; many are generalist predators that opportunistically consume spiders for food. Praying mantises are ambush predators that readily include spiders in their diet. They rely on camouflage and speed, using their powerful, spiked raptorial forelegs to snatch the spider and begin eating it immediately.
Assassin bugs, members of the family Reduviidae, also hunt spiders using stealth and specialized techniques. Some species use aggressive mimicry, carefully plucking the silk threads to simulate the vibrations of trapped prey. This luring tactic draws the web’s owner into striking range, where the bug can inject its toxic, liquefying saliva. Other assassin bugs tap a spider with their antennae to disorient it before delivering a fatal venomous jab with their proboscis. Unlike the specialized wasps, these generalists kill and consume the spider directly.
The Biological Purpose: Paralysis and Larval Provisioning
The specialized hunting behavior of these wasps is driven by larval provisioning. The female wasp’s goal is to secure a living, fresh host for her single offspring, not to feed herself. After the sting paralyzes the spider, the wasp drags it to a nest, which is often a burrow dug in the soil or a pre-existing cavity.
The wasp then lays one egg on the spider’s abdomen before sealing the nest entrance. The spider is alive but immobile, rendered into a state of suspended animation by the venom. When the egg hatches, the larva begins to feed on the tissues of its host.
The larva’s feeding strategy is precise, ensuring the spider remains alive and fresh for the longest possible time. It consumes the non-essential tissues first, deliberately avoiding the spider’s vital organs, such as the heart and central nervous system. This preservation keeps the host from decomposing until the larva has fully matured. Once the larva has consumed the entire spider, it spins a cocoon and pupates, eventually emerging as an adult wasp.