Yes, spiders frequently eat other spiders, a behavior known as araneophagy, which translates to “spider-eating.” This phenomenon occurs both within a single species (cannibalism) and across different species (predation). The spider world is highly competitive, and a fellow spider represents a highly nutritious meal. This predatory behavior shapes everything from mating rituals to specialized hunting tactics.
Cannibalism: Eating Within the Same Species
Cannibalism, or intraspecific predation, is widespread among spiders and often occurs in specific contexts. The most well-known form is sexual cannibalism, where the female consumes the male before, during, or after copulation. In species like the Australian redback spider (Latrodectus hasselti), the male actively helps this process by somersaulting onto the female’s fangs during mating, which increases his paternity success. This act provides the female with a large nutritional boost, which is directly invested into the eggs she produces.
The roles can sometimes be reversed, though this is much less common and is known as male sexual cannibalism. Males of the wolf spider Allocosa brasiliensis sometimes consume smaller, less fertile older females, suggesting a form of adaptive foraging. This strategic consumption ensures the male does not waste time or energy attempting to mate with a female whose reproductive potential is low.
Cannibalism is not limited to mating, as it also affects younger generations through filial and sibling consumption. Immediately after hatching, spiderlings may eat their siblings or even their mother, a phenomenon often driven by resource scarcity. This reduces the number of competitors, ensuring the remaining spiderlings have a better chance of survival. Opportunistic cannibalism occurs when a spider is severely hungry or if a conspecific is injured or trapped.
Araneophagy: Specialized Spider Hunters
Some spider groups have evolved highly specialized methods for hunting other species. These hunters develop sophisticated tactics to overcome the defensive and sensory systems of their arachnid prey. Unlike generalist predators that might consume a smaller spider they encounter, specialized araneophagic spiders actively prefer other spiders over insects.
A prime example is the jumping spider genus Portia, known for its intelligence and predatory versatility. Portia species are web-invaders that use aggressive mimicry to deceive their prey. They approach a victim’s web and vibrate the silk in patterns that mimic the signals of an ensnared insect or a potential mate, luring the host spider close enough to be attacked.
Another group of specialized interspecific predators is the pirate spiders, or Mimetidae. Pirate spiders have extremely potent venom that quickly immobilizes their victims, which is necessary because they often attack spiders significantly larger than themselves. They, too, invade webs, sometimes plucking the silk to deceive the resident spider into approaching. This specialized hunting contrasts with generalist predators, such as larger wandering spiders, which will opportunistically consume smaller spiders they encounter.
Survival Strategies and Avoidance
Spiders possess a variety of physical and behavioral adaptations to avoid becoming a meal for a conspecific or a specialized hunter. One important defense mechanism is chemical signaling, which is particularly relevant in avoiding sexual cannibalism. Male spiders release specific pheromones to signal their gender and maturity, differentiating themselves from prey. These chemical cues help to pacify the female’s predatory instincts long enough for a successful courtship and mating to occur.
Physical defenses and behaviors also play a large role in evading araneophagic predators. Many spiders utilize cryptic coloration and background matching to blend into their environment, making them difficult for visually-oriented hunters to spot. Orb-weaving spiders may employ defensive postures when threatened, such as rapidly vibrating their web to blur their outline and confuse an attacker.
The placement and architecture of a spider’s web can also serve as a form of avoidance. Some spiders construct retreats or barrier webs, providing a physical refuge from predators. When suddenly disturbed, many web-builders will drop from the web on a silk safety line, a quick escape mechanism to evade an immediate attack.