The natural moth emergence-pattern of Diparopsis castanea Hmps. from non-diapause and diapause pupae is described for Malawi and Rhodesia and related to the growth of the cotton plant. Pupal populations and mortality in the field are assessed and the location of pupae in the soil for both ridged and flat land is determined. The effect of temperature on the development of diapause pupae is investigated. Temperatures both above and below 75°F. are shown to cause inhibition of pupal development. The investigations show that it is possible to effect a major alteration in the period of moth emergence from diapause pupae by burying the pupae to a depth of eight inches and thus avoiding heat inhibition. In this way, the majorrity of moths emerge before the cotton crop is able to support an infestation. Attempts to achieve this effect with a natural field population of pupae failed and further investigation is required. Heavy grass mulches are shown to inhibit pupal development possibly throgh reduction in soil temperature and retention of soil moisture.