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, multipl
