Acoustic Cues

In some cockroach species mating behavior is highly stereotyped, with an internally programmed, unidirec-

Fig. 6.4 Copulating pair of Macropanesthia rhinoceros, a species with type III mating behavior. Photo courtesy of Harley Rose.

tional sequence of acts (Bell et al., 1978); in others, malefemale interaction is more flexible (Fraser and Nelson, 1984). Variations that do occur often take the form of behaviors that produce airborne or substrate-borne vibrations, particularly when males are courting reluctant females (Fig. 6.5). These signals typically occur after antennal contact but prior to full tergal display, and include rocking, shaking, waggling, trembling, vibrating, pushing, bumping, wing pumping, wing fluttering, "pivot-trembling," anterior-posterior jerking, hissing, whistling, tapping, and stridulation. Although Barth (1968b) suggested that vibrating and wing fluttering during courtship produce air currents that serve to disseminate pheromone, very little is known regarding the role of these behaviors in influencing female receptivity. Hissing during courtship is best known in G. portentosa (Fraser and Nelson, 1984), but occurs in other species as well. Males of Australian burrowing cockroaches pulse the abdomen during courtship, and the behavior is accompanied by an audible hiss in the larger species (D. Rugg, pers. comm. to CAN). Elliptorhina chopardi males produce broad-band, amplitude-modulated hisses like G. portentosa, but also complex, bird-like whistles; dual harmonic series warble independently from the left and right fourth spiracle (Fraser and Nelson, 1982; Sueur and Aubin, 2006). The common name of Rhyparobia maderae is the "knocker" cockroach, because of the male habit of tapping the substrate with his thorax in the presence of potential mates (Fig. 6.5B). Highly developed stridulating organs are found on the pronotum and tegmina of some Blaberidae (Oxyhaloinae and Panchlorinae) (Roth and Hartman, 1967; Roth, 1968c).Males of Nauphoeta cinerea use the structures to produce characteristic phrases consisting of complex pulse trains and chirps if a female is unresponsive to his overtures (Hartman and Roth, 1967a, 1967b). There is currently no evidence, however, that the male's distinctive song (Fig. 6.5D) influences her response. Sounds produced by N. cinerea during courtship can be recorded from the substrate on which they are standing as well as by holding a microphone at close range (Roth and Hartman, 1967). Given the evidence that cockroaches can be sensitive to vibration as well as airborne sound (Shaw, 1994a), substrate-borne courtship signals may be more common than is currently appreciated. This is especially relevant for tropical cockroaches that perch at various levels in the canopy during their active period. Bell (1990) noted that cockroaches on leaves can detect the vibrations of approaching predators. These cockroach species also have potential for communicating with each other via leaf tremulation. The cockroach "ear" is the subgenual organ on the metathoracic legs, a fan-shaped structure lying inside and attached to the walls of the tibiae. The subgenual organ of P. americana is one of the

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Fig. 6.5 Oscilloscope records of sounds in cockroaches. (A) Arrhythmic rustling sound made by a courting male Eu-blaberus posticus; (B) sound produced by a male Rhyparobia maderae tapping upon the substrate, which in this case, was a female on which the male was standing; (C) courting sounds produced by a male Diploptera punctata by striking the wings against the abdomen; (D) phrase produced by stridulation during courtship in male Nauphoeta cinerea; compare to (E) disturbance sound made by male N. cinerea. After Roth and Hartman (1967); see original work for reference signals and sound levels.

Fig. 6.5 Oscilloscope records of sounds in cockroaches. (A) Arrhythmic rustling sound made by a courting male Eu-blaberus posticus; (B) sound produced by a male Rhyparobia maderae tapping upon the substrate, which in this case, was a female on which the male was standing; (C) courting sounds produced by a male Diploptera punctata by striking the wings against the abdomen; (D) phrase produced by stridulation during courtship in male Nauphoeta cinerea; compare to (E) disturbance sound made by male N. cinerea. After Roth and Hartman (1967); see original work for reference signals and sound levels.

most sensitive known insect vibration detectors (Autrum and Schneider, 1948; Howse, 1964).

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