On the hardening of the ootheca of Blatta orientalis

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Abstract
The ootheca of Blatta orientalis was chosen as the object of an investi­gation into the hardening mechanism of the insect cuticle because the material of which it is composed looks like the hard brown exocuticle of a typical insect. It is, however, secreted by glands, from which comparatively large amounts of the substances concerned can be obtained. The ootheca is about 8 mm. long, and has the shape of a carpet bag, opening by two flat adpressed lips, which have a regular pattern of ridges and hollows on them. Inside there are about a dozen elongated eggs, arranged in two rows. In the wall of the ootheca are embedded numerous crystals of calcium oxalate (Hallez 1909). The function, if any, of these crystals is obscure; they may help to harden the wall, or they may simply be excretory products, since Sinéty (1901) has recorded crystals of an oxalate from the Malpighian tubules of a phasmid.