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

male of Eub. posticus “raises up on his forelegs and makes
rhythmic pushing movements of his abdomen in a pulsating
fashion” (Wendelken and Barth, 1987). Diploptera
punctata males move their abdomen from side to side just
prior to releasing the female (Roth and Stay, 1961). Conversely,
females of Parc. fulvescens assume an arched posture
during copulation, and rhythmical movements were
observed for which the female appeared responsible
(Wendelken and Barth, 1971). In addition to internally
stimulating the female with genital structures, males may
sing, tap, rub, hit, kick, wave, lick, wet with secretions,
bite, feed, rock, and shake females in attempting to influence
cryptic choice decisions (Eberhard, 1996). The production
of oral liquid during mating by male Parc. fulvescens
was listed by Eberhard (1991) as a form of
copulatory courtship. A repeating sequence of pronotal
butting, abdominal wagging, and circling behavior has
been observed in C. punctulatus after genital disengagement
(Nalepa, 1988a) and has been interpreted by Eberhard
(1991) as post-copulatory courtship.
Reduction and Loss of Genitalic Structures
The genital phallomeres of some blaberid cockroaches
are lightly sclerotized, considerably reduced, or in some
cases, altogether absent. The Panchlorinae are characterized
by the absence of a genital hook, and if the remaining
two phallomeres are present, they are markedly reduced
(Roth, 1971b). Likewise, one or more phallomeres
may be reduced or absent in many Panesthiinae (including
Geoscapheini) (Fig. 6.11D) (Roth, 1977). Macropanesthia
rhinoceros and M. heppleorum males completely
lack a genital hook, and sclerites L1 and L2d
are also missing. Some of the Australian soil-burrowing
cockroaches exhibit intraspecific variation in the reduction
of phallomeres (Walker and Rose, 1998). The occurrence
of poorly developed male genitalia in cockroaches
corresponds very well with copulatory behavior. A reduced
or absent genital hook is strong evidence of type III
mating behavior, that is, the male backs into the female to
initiate mating (Roth, 1971b, 1977).
Simple genital structure in males is predicted by the
cryptic choice hypothesis if females are monandrous, because
sexual selection by female choice is possible only if
females make genitalic contact with more than one male
(Eberhard, 1985, 1996). In monandrous females, the
choice of sire is settled prior to copulation, via mechanisms
such as premating courtship or male-male contests.
The mating strategy in cockroaches with reduced
genitalia is not known well enough to determine if that is
the case here; however, one male is usually present in social
groups of Panesthia. Panesthia cribrata typically lives
in aggregations, often (29%) comprised of a single adult
male, a number of adult females, and nymphs of various
sizes (Rugg and Rose, 1984a).
Additional correlates of reduced male genitalia in
cockroaches also must be considered. Among the Panesthiinae
species studied, the absence of an oothecal covering
around the eggs is correlated with the absence or reduction
of male genital structures (Walker and Rose,
1998). All of the species for which we have information
also exhibit a burrowing lifestyle, tunneling in soil, rotted
wood, or rotted palms. How all these threads connect
(burrowing lifestyle, mating system, copulatory behavior,
male genital morphology, and absence of egg case) awaits
further study. It is of interest (Chapter 9), however, that
termites are monogamous (Nalepa and Jones, 1991) and
that isopteran males are largely unencumbered by genitalia
(Roonwal, 1970). Termites also live in burrows, mate
by backing into each other, and except for Mastotermes,
have lost the casing around their eggs. Species in the
Cryptocercidae, the sister group of termites, live in burrows
and are apparently monandrous, but male genitalia
are not markedly reduced; they do, however, exhibit a
number of paedomorphic characters (Klass, 1997).
THE FEMALE PERSPECTIVE
A variety of female traits can bias paternity, including the
premature interruption of copulation and the acceptance
or rejection of matings from additional males. Females
may also accept a male for copulation but reject him as a
father. This is possible because insemination and fertilization
are uncoupled in space and time (Eberhard,
1985), and because females have many opportunities to
modify the probability that a given copulation will result
in egg fertilization. There are at least 20 different mechanisms
that can result in cryptic female choice (Eberhard,
1994, 1996), many of which may apply to cockroaches.
These include sperm transport to storage sites, sperm
nourishment during storage, the ability to discharge or
digest stored sperm, and the biased use of stored sperm to
effect fertilization, particularly in females with multiple
spermathecae. Sperm selection may even occur at the site
of fertilization; Eberhard (1996) gives as an example Periplaneta,
which has up to 100 micropyles for sperm entry
at one end of the egg (Davey, 1965). After fertilization
ovoviviparous females may abort the egg case. The multiplicity
of female mechanisms reduces the likelihood
that males will be able to evolve overall control of female
reproductive processes, even if males try to prevent further
matings via genital plugs, mate guarding, or induced
unreceptivity (Eberhard, 1996). While there are no available
studies that directly address cryptic choice in female
MATING STRATEGIES 105