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

that her increased activity level initiates it (D. E. Mullins
and K. R. Tignor, pers. comm. to CAN).
Oviparity type B occurs in two subfamilies of Blattellidae.
In the Blattellinae, at least nine species of Blattella
and one species of the closely related Chorisia exhibit this
reproductive mode (Roth, 1985). In the Pseudophyllodromiinae
two species of Lophoblatta carry their oothecae
externally throughout gestation. The first of these was
found by LMR in the Amazon basin in 1967; a female
Loph. brevis carrying an ootheca was collected on a banana
plant, and the eggs hatched the following day. A second
species with external egg retention, Loph. arlei, was
taken from a bird nest. All other known Lophoblatta deposit
their oothecae shortly after they are formed (Roth,
1968b).
OVOVIVIPARITY
Fig. 7.4 Scanning electron microscopy images of Blattella germanica
oothecae, demonstrating the morphological basis of
their permeability. (A) Proximal end of an ootheca showing the
“escutcheon-shaped” vaginal imprint (arrow). (B) Magnification
of the ventro-lateral escutcheon region; arrow indicates
the pore field area. (C) Magnification of the pore-field area. (D)
Pores. From Mullins et al. (2002), with permission from The
Journal of Experimental Biology. Images courtesy of Donald
and June Mullins.
found in the wrinkled region surrounding the “escutcheon-shaped”
vaginal imprint on the proximal end
(Mullins et al., 2002).
Because the barrier between mother and developing
embryos is permeable, females that externally carry egg
cases throughout gestation have the advantage of parceling
water and other soluble materials to the embryos on
an “as needed” basis. They also have some degree of behavioral
control over the embryonic environment.
Nymphs of B. germanica are known to settle in microhabitats
where temperatures are favorable to their development
(Ross and Mullins, 1995); it is probable that a female
carrying an egg case acts similarly on behalf of her
embryos. In most instances, hatch of the egg case is initiated
while it is still attached to the mother. The activity
level of the female increases significantly prior to hatch,
indicating either that she can detect impending hatch, or
Ovoviviparity occurs in all Blaberidae except the viviparous
Diploptera punctata, and in four genera of Blattellidae:
Sliferia, Pseudobalta (Pseudophyllodromiinae)
(Roth, 1989a, 1996), Stayella, and Pseudoanaplectinia (Blattellinae)
(Roth, 1984, 1995c). As in oviparous cockroaches,
type A ovoviviparous species extrude the ootheca as it is
being formed. When oviposition is complete, however,
the egg case is retracted back into the body and incubated
internally in a type of uterus, the brood sac, throughout
development. The brood sac is an elaboration of the
membrane found below the laterosternal shelf in oviparous
cockroaches and is capable of enormous distension
during gestation (Fig. 6.14). The eggs have sufficient
yolk, but must absorb water from the female to complete
development. At hatch, the nymphs are expelled from this
maternal brood chamber, and quickly shed their embryonic
cuticle. There is some evidence that pressure exerted
by the female on the ootheca during extrusion supplies
the hatching stimulus (Nutting, 1953a).
Ovoviviparous females are thought to provide only water
and protection to embryos during gestation, with the
yolk serving as the main source of energy and nutrients.
This is supported by data indicating that in ovoviviparous
Rhyparobia maderae and Nauphoeta cinerea, water content
increases and dry weight decreases during embryogenesis,
just as it does in oviparous P. americana (Roth
and Willis, 1955c; Roth, 1970a). Even if it is not reflected
as weight gain, however, ovoviviparous cockroaches may
be supplying more than water to their retained embryos.
This is suggested by the physiological intimacy of the embryonic
and maternal tissues, and the evidence that maternal
transfer of materials occurs in oviparous B. germanica.
Based on morphological evidence, Snart et al.
(1984a, 1984b) suggested that Byrsotria fumigata and
Gromphadorhina portentosa, two Blaberidae commonly
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