The scent glands of Opiliones: a review of their function.

Abstract

Opilionids are unique among the arachnids in that they possess a pair of glands that open dorsally near the lateral edge of the prosoma. These glands are variously called scent, odoriferous, repugnatory, or stink glands and generally have been considered as a defensive mechanism against predators. Theoretically, the glands may function in several ways such as in waste removal, protection from microorganisms, repulsion of predators and parasites, intraspecific recognition, and sexual, alarm, and aggregation behaviors. In actuality, only two functions have been proven-predator defense and aggregation formation. Many of the chemicals found in the secretions of scent glands effectively deter attacks by ants. Indeed some of these chemicals are ant alarm pheromones. Other evidence for predator repulsion is very fragmentary and often based on single observations. Though opilionids are typically solitary, some species form aggregations that may consist of thousands of individuals. In at least one species of Leiobuninae, scent-gland secretions promote aggregation behavior. As more work is done on opilionid scent glands, multiple