Gallery Initiation and Male Stridulation of the Polygamous Spruce Bark Beetle Polygraphus rufipennis1, 2

Abstract

The polygamous bark beetle Polygraphus rufipennis has an anomalous pattern of gallery initiation and stridulation. Though more often the male attacks the host, either sex can initiate a gallery and be joined by the opposite sex. The nuptial chamber is constructed only by the male. Unlike other polygamous Scolytidae known, to stridulate, males have an elytral-abdominal stridulatory file and plectrum, but females do not. No differences were found in measured parameters of male chirps produced in stress, attraction, and rivalry contexts. Attracted females rub their mandibles against the elytra of males guarding the nuptial chamber entry; neither sex stridulates during this behavior. Male stridulation in this species may be an evolutionary holdover from a monogamous ancestor.