Courtship And Copulation

Once in the vicinity of a potential mate, contact phero-mones on the surface of the female and short-range volatiles produced by the male facilitate sexual and species recognition and coordinate courtship. Recently the topic was comprehensively reviewed by Gemeno and Schal (2004). Developments in the field worth noting include the finding that short-range and contact pheromones not only mediate mate choice and serve as behavioral releasers during courtship, but may regulate physiological processes as well. The phenomenon is best studied in Nauphoeta cinerea, where male pheromones may influence female longevity, the number and sex ratio of offspring, and their rate of development in the brood sac (Moore et al., 2001,2002,2003).

FEMALE MALE

Motionless

Fig. 6.3 "Basics" of type I courtship and copulation in cockroaches, after initial orientation to a potential mate.

With few exceptions, pre-copulatory behavior is remarkably uniform among cockroaches (Roth and Willis, 1954b; Roth and Dateo, 1966; Roth and Barth, 1967; Roth, 1969; Simon and Barth, 1977a). Antennal contact with the female usually instigates a male tergal display (Fig. 6.3); he turns away from her and presents the dorsal surface of his abdomen. The female responds by climbing onto his back and "licks" it, with the palps and mouth-parts closely applied and working vigorously. The "female above" position lasts but a few seconds before the male backs up and extends a genitalic hook that engages a small sclerite in front of her ovipositor. Once securely connected, he moves forward, triggering the female to rotate 180 degrees off his back. The male abdomen untwists and recovers its normal dorsoventral relationship almost immediately. The pair remains in the opposed position until copulation is terminated.

Although the final position assumed by cockroaches in copula is invariably end to end, there are two additional behavioral sequences that may precede it. Both are characterized by the lack of a wing-raising display and female feeding behavior.

Type II mating behavior is characterized by the male riding the female, and is known in Pycnoscelus indicus and Jagrehnia madecassa. After the male contacts the female he crawls directly onto her back. He twists the tip of his abdomen down and under that of the female, engages her genitalia, then dismounts and assumes the opposed position (Roth and Willis, 1958b; Roth, 1970a; Sreng, 1993). In type III pre-copulatory behavior, neither sex mounts the other. After contact is made between the sexes, the male typically positions himself behind the female with his head facing in the opposite direction, then moves backward until genitalic contact is established. Cockroaches that fall into this category include Grompha-dorhinaportentosa (Barth, 1968c), Panchlora nivea (Roth and Willis, 1958b), Pan. irrorata (Willis, 1966), The.peti-veriana (Livingstone and Ramani, 1978), Panesthia aus-tralis (Roth, 1979c), and the giant burrowing cockroach Macropanesthia rhinoceros. Mating in the latter has been described as being "like two Fiats backing into each other" (D. Rugg, pers. comm. to CAN) (Fig. 6.4). In Epi-lampra involucris, the male arches his abdomen down and then up in a sweeping motion until he contacts the female's genitalia (Fisk and Schal, 1981). In Panesthia cri-brata, the two sexes start out side by side. The female raises the tip of her abdomen and the male bends toward the female until the tips of their abdomens are in close proximity. The male then turns 180 degrees to make genital contact (Rugg, 1987). It is of interest that type III pre-copulatory behavior occurs in the Polyphagidae (Therea), and in four different subfamilies of Blaberidae. A common thread is that most of these cockroaches are strong burrowers, suggesting that the behavior may be an adaptation to some aspect of their enclosed lifestyle. It is also notable that termites initiate copulation by backing into each other (Nutting, 1969).

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