Studies on the isolation of diapause and non-diapause strains of Trogoderma granarium everts (Coleoptera,Dermestidae)

By continuous mass selection and inbreeding, populations of Trogoderma granarium larvae that showed nearly 100 per cent incidence of diapause or 100 per cent freedom from diapause when reared in isolated or crowded conditions on wheat flour at 30°C, were obtained. The progress of selection showed that diapause is a polygenic character. The density-dependent diapause was manifested even in populations in which the density-independent diapause was totally eliminated by selection. In standard experimental populations most larvae enter diapause at 30°C and pupate promptly at 35°C when reared in isolation on a suboptimal diet viz. wetted-dried wheat flour. In contrast, the selected non-diapause population neither entered diapause at 30°C nor pupated at 35°C when fed on this diet; instead, at both the temperatures most larvae either died in the first stadium or survived for long periods with little gain in weight.