Female Receptivity

Female cockroaches have strong control of the courtship and mating process; there are several points in the behavioral sequence when she can terminate the transaction. In those cockroach species where females produce volatile pheromones, she may not call; if males produce the pheromones, she may not respond. Females may refuse to mount and feed on the tergites of a displaying male, but if she does, she may not allow genitalic engagement. If she does allow genitalic engagement, she may terminate copulation prematurely. A female's attractiveness to potential mates and her response to sexual overtures from them may or may not be congruent (Brousse-Gaury, 1977). Males of Su. longipalpa, for example, begin courting females 8 or 9 days after the female's imaginal molt. Females of this age do not respond to male sexual displays nor do they mate. Female calling and sexual receptivity are initiated 11 to 15 days after adult emergence. A lack of calling behavior in mature females, however, does not necessarily mean that they are unreceptive; 8% will mate if courted (Hales and Breed, 1983).

Response to Courtship

In most species newly emerged females require a period of maturation before they will accept mates. Virgin females of N. cinerea, R. maderae, and Byr. fumigata become receptive at an average of 4, 9, and 15 days, respectively (Roth and Barth, 1964). Eublaberusposticus females mate just after emergence, after their wings have expanded but before the cuticle has hardened (Roth, 1968c). Jagrehnia madecassa (Sreng, 1993), Neostylopyga rhombifolia (Roth and Willis, 1956), and D. punctata (Roth and Willis, 1955a) females are receptive when they are freshly emerged, pale, and teneral. The latter have a narrow window of opportunity for copulation; most that are isolated for several days following emergence do not mate when they are eventually exposed to males (Stay and Roth, 1958). In N. cinerea, younger females require longer periods of courtship prior to copulation than do older ones (Moore and Moore, 2001).

Females display their lack of receptivity to courting males in a variety of ways. A Parc. fulvescens female uninterested in mating decamps immediately upon contacting the male (Wendelken and Barth, 1971). Unreceptive blaberid females commonly flatten themselves against the substratum with their antennae tucked under their body

(e.g., Byr. fumigata—Barth, 1964). Blaberus females will lower the pronotum or the entire body (Grillou, 1973), tilt the body down on the side facing the male, or kick at courting males (Wendelken and Barth, 1987). Some blat-tid females can be aggressively unreceptive, and escalate their belligerent behavior when courted by highly motivated males. Occasionally persistence pays off; females sometimes gradually shift to a less aggressive, more receptive pattern of behavior (Simon and Barth, 1977b). Aggression by males directed against unreceptive females is infrequent. Blaberus giganteus males occasionally bite an unreceptive female's wings (Wendelken and Barth, 1987), but forced copulation by males cannot occur in species where mating is dependent on female mounting and feeding behavior (Roth and Barth, 1964).

Copulation Refusal

Females often mount and feed on the tergal glands of courting males, but refuse to allow genitalic engagement. The nature of tergal secretions may be at least in part responsible; in the German cockroach the secretions smell like food and thus may lure hungry females regardless of their interest in mating. After mounting and feeding, a cooperative female orients her abdomen and opens her genital atrium to facilitate interaction with male genitalia (Roth and Willis, 1952a). Alignment of the two abdominal tips can require considerable female adjustment, particularly in species where she is larger than the male. Byr-sotria fumigata females flex the abdominal tip forward ventrally so that genital connection can be made (Barth, 1964) and Blab. craniifer females may partially dismount in an attempt to improve the orientation of the genitalia (Wendelken and Barth, 1987). Cooperative females also open wide to allow full genital access. In Eur. floridana the gape of a receptive female's genital atrium is so impressive that the male can insert the entire tip of his abdomen (Barth, 1968b). Species in which the sexes back into each other also require female cooperation to copulate successfully. Panesthia cribrata females raise the tip of the abdomen and open the posterior plates (O'Neill et al., 1987).

After the genitalia are engaged, there are three major points at which a pair may separate: during turning to the opposed position, a few seconds after turning, and during the first 15 min of copulation. The signal to assume the opposed position comes from the male. He moves slightly forward, and the female responds by rotating off his back. If the female initiates the turning, it invariably results in separation of the pair (Simon and Barth, 1977a). After assuming the opposed position, brief genitalic connections of 4-7 sec are not uncommon in B. germanica (Roth and Willis, 1952a). Eublaberus posticus females frequently kick at the point of intersexual juncture with their metathoracic legs (Wendelken and Barth,

1987). In 12% of copulations of D. punctata observed by Wyttenbach and Eisner (2001), the teneral female pushed at the male with her hind legs until he disengaged; in each case the female subsequently accepted a second male. Females of N. cinerea require a longer period of courtship prior to copulation if they can detect the chemical traces of former female consorts on a male (Harris and Moore, 2005)—the cockroach equivalent of lipstick on his collar. After genitalic engagement, they can apparently determine if a male is depleted of sperm or seminal products because of those recent matings. After the first copulation "males are less adept at grasping the female," and pairs often remained joined for only a few seconds or minutes; no spermatophore is transferred. The female pushes the male with her hind legs, forcing him to release her (Roth, 1964b). Further evidence of female control of copulation in N. cinerea comes from transection experiments. When female genitalia were denervated males could not grasp the female properly and they stayed connected for only a few seconds (Roth, 1962).

Copulatory Success

Several studies report that male B. germanica have an abysmal record of successfully courting and copulating with females provided to them. Curtis et al. (2000) exposed each of 9 virgin males to serial batches of 2-10 virgin females throughout their lifetime (total of 341 females). Only 27 females were successfully inseminated. One-third of the males sired no offspring, and a further third inseminated just a single female. In a study of 55 virgin pairs by Nojima et al. (1999b), 84% of males courted females, 65% of the females responded by tergal feeding, but only 37% made the transition to copulation. Roth and Willis (1952a) did a detailed analysis of courtship and copulation in 10 pairs of German cockroaches (Table 6.2). Males courted rather vigorously in most cases; male 8, for example, courted the female 48 times in 30 min. Four females (pairs 3,4,5,10) were nearly or completely unresponsive to male courtship, and 5 females responded by tergal feeding but refused to mate (pairs 2, 6-9). Just one of the 10 observed pairs successfully copulated. This puzzling lack of copulatory success has been noted in at least 2 other cockroach species. O'Neill et al. (1987) reported that in the majority of observed courtships, females of Pane. cribrata (Blaberidae) were not receptive. Males of P. americana (Blattidae) are rarely readily acceptable to the female (Gupta, 1947); only one in 20 attempted matings appeared successful in Rau's (1940) study of the species.

Female Loss of Receptivity

Although female sexual receptivity is inhibited as a result of mating in all cockroach species studied (Barth, 1968a), the fine points of its physiological control are far from straightforward. Not only do details of regulation differ among species, but the various components of mating behavior are controlled in distinct ways within a species (Roth and Barth, 1964). "It is essential to be wary of generalization" (Grillou, 1973). Mechanical cues are of primary importance in examined cockroaches, but chemical influences cannot always be ruled out (Engelmann, 1970). Interaction with male genitalia, the presence of the spermatophore in the female genital tract, and sperm or seminal fluid in the spermathecae have all been reported as mechanical cues influential in the initial or sustained loss of receptivity in cockroaches following mating (Roth and Stay, 1961; Roth, 1964b; Stay and Gelperin, 1966; Smith and Schal, 1990; Liang and Schal, 1994). The phenomenon is best studied in three cockroach species, the blattellids B. germanica and Su. longipalpa, and the bla-berid N. cinerea. In the blattellids, one aspect of female receptivity, calling, is turned off by two successive mechanical cues provided by males during copulation. First, the insertion of a spermatophore results in the immediate cessation of calling. The behavior can be suppressed in experimental females by a spermatophore in the genital tract, by the insertion of a fake spermatophore, and by copulation with vasectomized males. The spermatophore effect, however, is transient. The presence of sperm or seminal fluids in the spermathecae is the stimulus that maintains the suppression of calling behavior in the first as well as the second ovarian cycles. The ventral nerve cord plays a crucial role in the transmission of the inhibitory signals (Smith and Schal, 1990; Liang and Schal, 1994). Signals transferred via the nerve cord also decrease locomotor activity in females (Lin and Lee, 1998).

The suppression of receptivity in N. cinerea following mating requires a single cue: mechanical stimulation caused by the insertion of the spermatophore into the bursa copulatrix (Roth, 1962, 1964b). The insertion of glass beads into the bursa results in the same loss of receptivity, manifested as a lack of a feeding response to male tergal displays. Spermatophore removal experiments indicate that female receptivity is lost immediately after the male reproductive product is firmly inserted into the bursa but prior to the migration of sperm into the sper-matheca. Cutting the nerve cord above the last abdominal ganglion in N. cinerea renders the female "permanently" receptive. However, it is curious that the ventral nerve cord in most females must remain intact for two days for female receptivity to be inhibited. Vidlicka and Huckova's (1993) finding that female N. cinerea become unresponsive to male sex pheromone about 2 days after mating is consistent with the results of these transection studies. Roth (1970b) suggests the possibility that mating stimuli are transmitted rapidly to the last abdominal gan glion but require a longer period to reach the brain, or that there is another source of stimulation in the genital region. If firmly inserted spermatophores are removed from mated females, about 15% will mate again (Roth, 1964b).After copulation, females remain unreceptive until after partition, at which time most remate. The absence of sperm in the spermatheca does not influence the return of receptivity after the first oviposition (Roth, 1962, 1964a, 1964b).

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