Copulation generally takes place in dark, during night.
2. Formation and insemination:
3. Fertilization and formation of ootheca (egg):
Fertilization takes place within the vestibulum of the female genital pouch. The collaterial glands pour their secretions over the inner surface of the vestibulum to form the ootheca. Sixteen eggs are laid into a single ootheca. The eggs are arranged in a double row, assisted by the ovipositor valves, very much like cigarettes in a cigarette case.
The sperms, stored in the spermatheca, fertilize the eggs when they pass from the vagina into the vestibulum for inclusion in the ootheca. More and more secretions from the collaterial glands harden the ootheca which is first white in colour but becomes pink later on. The ootheca is oblong in shape with a keel on its outer dorsal fringe.
4. Laying of ootheca (egg):
The female cockroach carries the ootheca, protruding from the tip of the abdomen, for several days, till it is deposited in a warm, sheltered and dark place.
5. Early embryonic development:
The ootheca which is laid at a suitable place by the female cockroach contains fertilized eggs. These are slightly curved, concave on one side and convex on the other. Each contains a diploid nucleus and yolk, the food for embryonic development. Each egg first undergoes cleavage resulting in a blastula, which is followed by a gastrula formation. The gastrula is differentiated into an early embryo which gets separated from the blastoderm by an amniotic cavity. Its three germ layers (the ectoderm, mesoderm and endoderm) the various parts of the nymph.
When hatching occurs, the dorsal keel of the ootheca splits and the nymphs emerge out leaving the egg membranes within the ootheca. The freshly-hatched nymphs are delicate, transparent and almost colorless creatures with black eyes. They possess nearly all adult characters but differ in size and colouration, in being sexually immature and lacking wings.
Immediately after hatching, the nymphs undergo first moulting or ecdysis and then five or six successive moults follow. As nymphal development proceeds, the wing pads arise, body increases in size, colouration becomes darker and ultimately the takes its form with fully developed wings and genitalia.
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