Signaling by Protrusive Scent Glands in Cave Crickets, Troglophilus neglectus Krauss (Orthoptera: Rhaphidophoridae), is Primarily Involved in Male-male Agonism

Abstract

Males of several species of cave crickets (Rhaphidophoridae) possess protrusive abdominal scent glands, which are generally presumed to influence female behavior before mating. The validity of this hypothesis, as well as of the alternative possibility of the signal being designed for the rivals, was tested in Troglophilus neglectus by describing the detailed context and the consequences of such signaling by gland protrusion in the mating period. Small groups of both sexes were observed under naturalistic conditions, using interval and focal behavioral sampling. The frequency of gland protrusion increased progressively in both experimental seasons, and was expressed in solitary males as well as in their interactions with both mates and rivals. Such signaling, however, was not an obligatory part of courtship and pre-mating behavior in general, and caused neither female attraction nor influenced the courtship success. The males protruded the glands significantly more frequently during the antennal contacts with another male than during contacts with a female. Of the different behaviors expressed in the inter-male encounters, only aggressiveness was significantly correlated with protrusion of the glands in the respective individuals. This strongly implies the function of the male scent as an agonistic signal, influencing the outcome of the intermale contests.