The Life-history and Growth of the CockroachBlatta orientalis, Linn.

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Abstract
The life-history ofBlatta orientalishas been studied from the time of the deposition of the ootheca by the female till the nymphs of the third generation emerge,viz., through two embryonic and one post-embryonic lives.The cockroach passes through one pronymphal and six nymphal stages and moults seven times after its exit from the ootheca.The post-embryonic growth, including the increase of the antennal and cercal joints, and the modification of the external genitalia, is described. It has been shown that nymphs of various instars and their sexes can be distinguished, especially with the help of the genitalia, the number of cercal joints, and the growth of the wing-rudiments.The average time taken by 27 nymphs to mature at 27·5C. is 279 days. The males mature earlier than the females and also die before the latter.The formation and structure of the spermatophore are described and also the exact mode of copulation, including the use of various parts of the male genitalia.The ootheca is deposited with special care by the female in that she digs a pit with the help of her mandibles and the fore legs and covers the ootheca afterwards. The nymphs emerge without the help of the female and the latter does not take any care of the ootheca after it has been safely deposited.