Some aspects of the biology of two species of Cryptolestes, with special reference to the effect of particle size of food

Abstract

The life cycle of C. turcicus has been described briefly. Distribution of the species shows that C. turcicus is predominent in the northern hemisphere. Experiments carried out at two humidities and three temperatures, on different particle sizes of wheat show, that development is quicker on coarser particles for C. ferrugineus, and on finer particles for C. turcicus. Increase of temperature was found to decrease the developmental period of both species, but at 32.5° C high mortality of C. turcicus occurred. Low humidity affects the development of C. turcicus more than that of C. ferrugineus; on whole grain larval mortality was 100% in C. turcicus, but about 60% in C. ferrugineus. The developmental period of individual stages has been determined at two temperatures and humidities. The calculated lower limiting temperature for the development of the egg, at about 64% R.H. is between 12-13 C for C. turcicus, and 15-16° 0 for C. ferrugineus. Brief experiments show that the preferred humidity range for each species is different; and that both species cannot attack whole sound grain. Observations on larval moulting, cocoon formation and locomotion were made; and the copulation frequency and pre-oviposition period were determined experimentally. The particle size of the food, the behaviour of the beetles, together with temperature-humidity conditions prevailing, seem to determine the differential distribution of the two species on stored products. The life history of a gregarine, probably a new species, found in the larval gut of C. ferrugineus has been determined. In C. turcicus, a cephaline gregarine reported for the first time, is parasitic in the larva and. is probably the same species as that found in C. ferrugineus.