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

occur once or twice a day” but give no further details. On
rare occasions, a female of Diploptera punctata may be
found carrying two spermatophores; however, one of
these is always improperly positioned (Graves, 1969).
Sperm are likely transferred only from the one correctly
aligned with the female’s spermathecal openings (discussed
below).
MATE FINDING
Most cockroaches that have been studied rely on chemical
and tactile cues to find their mates in the dark (Roth
and Willis, 1952a). In many cases volatile sex pheromones
mediate the initial orientation; these have been demonstrated
in 16 cockroach species in three families. The
pheromones are most commonly female generated and
function at a variety of distances, up to 2 m or more, depending
on the species (Gemeno and Schal, 2004). Females
in the process of releasing pheromone (“calling”)
often assume a characteristic posture (Fig. 6.1): they raise
the wings (if they have them), lower the abdomen, and
open the terminal abdominal segments to expose the genital
vestibulum (Hales and Breed, 1983; Gemeno et al.,
2003). In some species the initial roles are reversed, with
males assuming a characteristic stance while luring females
(Roth and Dateo, 1966; Sreng, 1979a). A calling
male may maintain the posture for 2 or more hr, with
many short interruptions (Sirugue et al., 1992). Based on
the limited available data, the general pattern appears to
be that in species where the male or both sexes are volant,
females release a long-range volatile pheromone. Males
release sex pheromones in species where neither sex can
fly (Gemeno and Schal, 2004).
Non-chemical Cues
Fig. 6.1 Calling behavior in female Parcoblatta lata. Females in
the calling posture raise the body up from the substrate and alternate
between two positions: (A) upward with longitudinal
compression, and (B) downward with longitudinal extension.
From Gemeno et al. (2003), courtesy of César Gemeno, with
permission of Journal of Chemical Ecology.
Fig. 6.2 Male Lucihormetica fenestrata Zompro & Fritzsche,
1999 (holotype) exhibiting its pronotal “headlights.” Copyright
O. Zompro, courtesy of O. Zompro.
While research has focused primarily on chemical cues
(and justly so), mate finding and courtship may be multimodal
in a number of species, that is, they integrate
chemical, visual, tactile, and acoustic signals. Vision apparently
plays little or no significant role in sexual recognition,
courtship, or copulation in the species typically
studied in laboratory culture (Roth and Willis, 1952a).
However, in many cockroaches the males have large, welldeveloped,
pigmented eyes, suggesting the possibility that
optical cues may be integrated with pheromonal stimuli
during mate seeking and mating behavior. Visual orientation
seems particularly likely in Australian Polyzosteriinae
and in brightly colored, diurnally active blattellids.
The delightful discovery of pronotal headlights on males
of Lucihormetica fenestrata suggests that even nocturnally
active cockroaches may use sight in attracting or courting
mates (Zompro and Fritzsche, 1999). This species lives in
bromeliads in the Brazilian rainforest and has two elevated,
kidney-shaped, strongly luminescent organs on the
pronotum (Fig. 6.2). These protuberances are highly
porous (probably to allow gas exchange) and absent in
nymphs and females. Males of several related species
sport similar structures, but because live material had
never been examined, their function as lamps was unknown.
COURTSHIP AND COPULATION
Once in the vicinity of a potential mate, contact pheromones
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).
MATING STRATEGIES 91