Heliothis armigera (Hb.) (Noctuidae) in Western Tanganyika. I.—Biology, with special reference to the pupal stage

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Abstract
In laboratory studies of Heliothis armigera (Hb.) in Western Tanganyika, where it may attack cotton severely, pairs of newly emerged adults, derived from sixth-instar larvae collected in the field and allowed to pupate in the laboratory, were confined separately and provided with sucrose solution. The mean number of eggs laid per female fell from 1,226 in March-May to 198 in June—July 1962. Peak egg laying occurred in the fifth to eighth nights after emergence. In April, the mean length of life of adults of either sex was about 11 days and the maximum one month. The mean incubation period of 1,436 eggs laid in March was 2·78 days, and 66 per cent. of them hatched. The mean period from hatching to pupation of 42 larvae reared on cotton squares in April was 21·1 days; each passed through six instars and required three squares in the first 14 days and a further 10 thereafter; only 22 per cent. of the dry weight of the squares was consumed and of this only nine per cent. was converted to pupal dry weight. Pupation occurs in the soil. The mean pupal period of males increased from 16 days in March to 18 in July, and their pupal weights fell from about 0·27 to 0·23 mg. over the same period, although at any given time pupal period was positively correlated with pupal weight. Female pupae were lighter than male pupae and had a shorter pupal period. From March to July, a small but progressively increasing proportion of the pupae formed entered diapause; the proportion averaged less than four per cent. in June to July 1962–64. The pupal period ranged from 30 to 171 days, being less in later-formed pupae, so that a general emergence occurred in September–late October.

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