Cockroache; Ecology, behavior & history - W.J. Bell

Fig. 6.11 Examples of variation in male genitalia. (A) Genitalia (dorsal) of Allacta australiensis
(Blattellidae: Pseudophyllodromiinae). Accessory median phallomere is broad, with an apical
brush-like modification (arrow). From Roth (1991d). (B) Subgenital plate and genitalia (dorsal)
of Hemithyrsocera nathani (Blattellidae: Blattellinae). A huge, sclerotized, densely setose brushlike
structure is found on the left side (arrow). From Roth (1995a). (C) Subgenital plate and genitalia
(dorsal) of Parasigmoidella atypicalis (Blattellidae: Blattellinae). Note distally curved median
phallomere with a pick-axe-like apex (arrow) and three-fingered “claw” on right. From Roth
(1999b). (D) Highly reduced phallomeres on the extruded aedeagal membrane of Panesthia
cribrata (Blaberidae: Panesthiine). From Walker and Rose (1998). Phallomeres are labeled according
to McKittrick’s (1964) classification. (E) Extraordinarily complex genitalia (dorsal) of
Homopteroidea nigra (Polyphagidae). From Roth (1995d).
blaberids, rivals disturb or attack courting or mating
males. Copulations may be broken off because of interference
in N. cinerea (Ewing, 1972). In B. craniifer males
assault copulating pairs by jumping on their backs and attacking
their point of juncture. The interference may
cause separation of the pair, but only if it occurs during
the first few seconds after they assume the opposed position.
The copulating male “shows no reluctance in fighting
with the intruder,” and “the trio may careen about the
mating chamber” (Wendelken and Barth, 1985, 1987). A
tight grasp of the female is also required because the pair
may travel during copulation. Pairs are usually quiescent
unless disturbed, in which case they move away. It is invariably
the female that is responsible for the locomotion,
dragging the passive male along in her wake (Roth and
Barth, 1967). She can move with astonishing speed,
pulling the “furiously backpedaling” male behind her (Simon
and Barth, 1977a). Blattella germanica (Roth and
Willis, 1952a), Byr. fumigata (Barth, 1964), Ell. humerale
( affine) (Pope, 1953), Latiblattella spp. (Willis, 1970),
Parcoblatta fulvescens (Wendelken and Barth, 1971), and
P. americana (Simon and Barth, 1977a) are among the
species in which this behavior has been reported. It also
occurs in G. portentosa, even though the male is much
heavier than the female (Barth, 1968c).
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-
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