Intromittent Organs

The need for a secure connection, then, may account for some of the claspers, hooks, and spines in the male's genitalic assemblage but cannot explain the bewildering complexity (Fig. 6.11E) of many components. The similarity of some cockroach structures to those of other, better-studied insects, however, allows us in some cases to make inferences from genitalic design. In particular, brushes and slender, elongate spines, rods, and flagellae, especially those with modified tips, may be sexually selected structures that increase a copulating male's fertil ization success. This may be accomplished in one of three basic ways: via the manipulation of rival sperm, by the circumvention of female control of sperm use, or via internal courtship of the female (Eberhard, 1985; Simmons, 2GG1).

A number of intromittent structures in male cockroaches have been called a penis, pseudopenis, phallus, or pseudophallus. Although these structures may be associated with the ejaculatory duct or have the appearance of organs specialized for penetration, sperm is transferred indirectly in cockroaches, via a spermatophore. Penis-like organs therefore function in some capacity other than to convey sperm directly from the testes of the male to the sperm storage organs of the female. In P. americana the pseudopenis, a structure of the left phallomere, is characterized as having a blunt, hammer-like tip and a thin dark ridge along its length (Bodenstein, 1953). According to Gupta (1947) the expanded tip of the pseudopenis enters the female gonopore (entry to the common oviduct) during copulation, and rotates 90 degrees on its own axis. In some Blattellidae (including Blattella) a conical membranous lobe between the right and left phallomeres is considered a penis. It is a posterior continuation of the ejac-ulatory duct and projects into the female genital chamber during copulation. A free spine, or virga, extends through the membranous wall of the penis above the gonopore. Snodgrass (1937) noted that males insert the virga into the female's spermathecal groove during copulation, and suggested that it functioned to guide the sperm of the copulating male to their storage destination. Because sperm remain in the spermatophore until after the pair disengages, however, the functional basis of the virga must be sought elsewhere. In Pseudophyllodromiinae, R3,a sclerite of the right phallomere, has an expanded anterior edge that is elongate, in some genera extraordinarily so. Most often it is curved and flat, but in Supella it is

Fig. 6.12 Diagrammatic representation of the external genitalia of Blattella germanica during copulation. (A) Side view of the initial position, female superior. The hooked left phallomere is extended and inserted into the genital chamber of the female. (B) The insects in the end-to-end position, ventral view. The paraprocts are holding the ovipositor from each side and the cleft scle-rite is holding it from the ventral side. The last sternite in both insects and the endophallus have been removed. After Khalifa (1950), with permission from the Royal Entomological Society. Labels of the various structures courtesy of K.-D. Klass.

Fig. 6.12 Diagrammatic representation of the external genitalia of Blattella germanica during copulation. (A) Side view of the initial position, female superior. The hooked left phallomere is extended and inserted into the genital chamber of the female. (B) The insects in the end-to-end position, ventral view. The paraprocts are holding the ovipositor from each side and the cleft scle-rite is holding it from the ventral side. The last sternite in both insects and the endophallus have been removed. After Khalifa (1950), with permission from the Royal Entomological Society. Labels of the various structures courtesy of K.-D. Klass.

Fig. 6.13 Male Chorisoserrata jendeki (Pseudophyllodromi-inae) (A) genitalia, (B) dorsal view of abdomen, and (C) ventral view of abdomen, demonstrating the genitalic filament, or whip, that projects from the abdomen. From VidliCka (2002), courtesy of the author and with permission from the journal Entomological Problems.

Fig. 6.13 Male Chorisoserrata jendeki (Pseudophyllodromi-inae) (A) genitalia, (B) dorsal view of abdomen, and (C) ventral view of abdomen, demonstrating the genitalic filament, or whip, that projects from the abdomen. From VidliCka (2002), courtesy of the author and with permission from the journal Entomological Problems.

flat and horseshoe shaped, and in Lophoblatta it forms a long whip-like structure (Fig. 113 in McKittrick, 1964). Male Chorisoserrata jendecki have a genitalic filament that dangles from the abdomen, like a tail (Fig. 6.13) (Vid-licka, 2002). Nahublattella, in the same subfamily, has a long whip as part of the left phallomere complex (Klass, 1997). Loboptera (Bohn, 1991a), Neoloboptera, and Non-dewittea (Roth, 1989b) (Blattellinae) have elongated filaments associated with the median phallomere complex. In males of the tortoise beetle Chelymorpha alternans, whips similar to these are threaded up the female's sper-mathecal duct during the early stages of copulation, and the length of the whip is related to the probability of fathering offspring (Rodriguez et al., 2004).

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