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

SEVEN
Reproduction
Be fruitful, and multiply, and replenish the Earth.
—Genesis 1:28
Perhaps no aspect of cockroach biology has been studied as extensively as the range of
mechanisms by which they replenish the earth. Understandably so, given that their variation
in this arena is a rich source of comparative material and that reproduction in many
species is amenable to laboratory study. Several reviews of cockroach reproduction are
available, including Roth and Willis (1954b, 1958a), Roth (1970a, 1974a), and Bell and
Adiyodi (1982b), among others.
In the majority of cockroaches, reproduction is characterized by the formation of an
ootheca: eggs are released from the ovaries, move down the oviducts, are oriented into two
rows by the ovipositor valves, then surrounded by a protective covering. Three general reproductive
categories are recognized, with two of these broken into subcategories (Table
7.1) (Roth, 1989a, 1991a, 2003c; Roth and Willis, 1954b, 1958a). In oviparity type A, females
drop the egg case shortly after formation. In oviparity type B, females carry the
ootheca externally throughout embryonic gestation, then drop it immediately prior to
hatch; eggs also may hatch while the ootheca is attached to the mother. Ovoviviparous females
gestate eggs internally, but the embryos rely primarily on yolk nutrients to fuel and
support development. In category A ovoviviparous females, the ootheca is first extruded,
as in oviparous taxa, but it remains attached and is retracted a short time later into a brood
sac. When the nymphs are ready to hatch, the ootheca is fully extruded and the neonates
emerge from their embryonic membranes. The eggs are deposited directly from the
oviducts into the brood sac in ovoviviparous type B species; there is no oothecal case. In viviparous
forms, oviposition is similar to the ovoviviparous type A cockroaches, but the embryos
are nourished within the brood sac on a proteinaceous fluid secreted by the mother.
OVIPARITY
Oviparous type A cockroach species characteristically produce an ootheca, a double row
of eggs completely enclosed by a protective outer shell (Stay, 1962; Roth, 1968a). A raised
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