Spider Cannibalism - Non-reproductive Cannibalism

Non-reproductive Cannibalism

Some spiders, such as Pholcus phalangioides, will prey on their own kind when food is scarce. Also, females of Phidippus johnsoni have been observed carrying dead males in their fangs. This behavior may be triggered by aggression, where females carry over hostility from their juvenile state and consume males just as they would prey. Sih and Johnson surmise that non-reproductive cannibalism can occur due to a remnant of an aggression trait in juvenile females. Known as the “aggressive spillover hypothesis”, this tendency to unselectively attack anything that moves is cultivated by a positive correlation between hostility, foraging capability, and fecundity. Aggression at a young age leads to an increase in prey consumption and as such, a larger adult size. This behavior “spills over” into adulthood, and shows up as a nonadaptive trait that manifests itself through adult females preying on males of their same species.