the eggs, or could possibly promote their maturation if it were. The temperature of the body of a cold blooded animal is always in equilibrium with the surrounding element, and it could, therefore, impart no additional heat to objects subjected to the same influence in this respect as itself. The case is different when multitudes are congregated within a narrow space; heat is then generated, as is well known to be the case in bee hives.
Fam. Blattidæ.
The members of this family are very unlike the preceding, and they may be said to differ nearly as much from all the other tribes with which they are associated. Their bodies are in general broad, oblong, and depressed, the abdomen almost completely covered by the tegmina, which considerably overlap each other on the back, and wholly cover the under wings. The head is curved inwards beneath the prothorax; the antennæ very long, setaceous, and flexible, inserted in a notch in the innerside of the eye; the two lower joints of the maxillary palpi are somewhat globular, the terminal one (as is likewise the case with the corresponding joint of the labial palpi,) pretty thick and truncated. A conical and articulated appendage projects from each side of the abdomen behind. The legs are thickly armed with spines on the tibia, and all the tarsi consist of five joints.
Most of these insects are of a uniform brown colour, a hue well adapted to their habits and the nature of their haunts. A few, which usually frequent flowers, are
