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

Fig. 7.7 Diagram of presumed sequence of stages in the evolution of ovoviviparity from oviparity in
two subfamilies of Blattellidae. Note the difference in the orientation of the ootheca between the two
subfamilies. Current evidence suggests that the oothecal rotation exhibited by the Blattellinae and by
the ovoviviparous Blaberidae originated in a common ancestor.
dwelling insect to carry or internalize must be either
squashed dorsoventrally or rotated so that it is as flat as
the female (Fig. 7.7). Intermediate stages in parity mode
are conspicuous in the Pseudophyllodromiinae. Sliferia
is considered ovoviviparous; nonetheless the egg case is
partially exposed while it is carried. Initially it was
thought that these females were collected while still forming
the ootheca. Now this condition is considered the
norm, and points up the continuum of reproductive
modes in this subfamily (Roth, 2003b).
All species in the ovoviviparous family Blaberidae
carry a rotated egg case in their brood sac and are thought
to have evolved from a Blattella-like ancestor (Roth and
Willis, 1955c; Roth, 1967a; Mullins et al., 2002). Except for
retraction of the egg case into the body, B. germanica exhibits
all characteristics of an ovoviviparous cockroach
(Roth and Willis, 1958a; Roth, 1970a). The oothecal case
is thinner and less darkly colored than in other oviparous
cockroaches, there is flow of water and other materials between
mother and unhatched offspring, and oogenesis is
suspended while females are carrying egg cases. The evolution
of ovoviviparity would require only a minor transition
from that starting point. Ovoviviparity evolved independently
two or three times in cockroaches, but only
in the blattellid/blaberid lineage (Roth, 1970a, 1989a):
once in the Pseudophyllodromiinae, and once or twice in
the clade that includes Blattellinae and Blaberidae. Viviparity
evolved once, in D. punctata of the monogeneric
subfamily Diplopterinae. Some authors also include Calolampra
or Phoetalia in this subfamily (Roth, 2003c), so
these genera may be logical targets for comparative study.
Worldwide, Blattellidae is the largest cockroach family
with about 1740 described species; there are approximately
1020 species of Blaberidae. The oviposition behavior
is known in relatively few genera and species of
these two families (Roth, 1982a).
Reduction and Loss of the Egg Case
In most oviparous type A cockroaches, the ootheca is a
hard, dark, stiff structure completely covering the eggs.
The dorsal keel is structurally complex, and the outer covering
contains calcium oxalate crystals. These crystals
comprise 8–15% of the dry weight of the ootheca in P.
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