THE INFLUENCE OF SOME FUNGI IN FLOUR, AND HUMIDITY ON THE SURVIVAL AND DEVELOPMENT OF CRYPTOLESTES TURCICUS (COLEOPTERA: CUCUJIDAE)

The flour mill insect, Cyrptolestes turcicus (Grouvelle), was reared on seven diets at 28 ± 1 °C and at relative humidities of 90% and 60% as follows: flour from a mill previously infested with C. turcicus, commercial flour sterilized with propylene oxide, unenriched commercial flour, and four laboratory-prepared diets each containing a different concentration of fungi isolated from the previously-infested flour.At 90% relative humidity, larvae developed fastest on the infested flour and on the prepared flour–fungi diets, and slowest in sterilized flour. Fungal concentration and rate of larval development were inversely correlated. The highest survival of larvae occurred on the flour–fungi diets and the highest mortality on the flour from the infested mill. There was no clear relationship between rate of pupal development and concentration of fungus. Of the prepared diets, that with the largest concentration of fungus promoted the fastest rate of pupal development. Survival of pupae was about 20% higher on the flour–fungi diets than on the sterilized flour. At 60% relative humidity about 50% of larvae and pupae survived and completed development on the flour–fungi diet containing 1% by weight of fungi, and on the flour from the infested mill but none survived on any of the other diets. Sixty per cent of larvae and 83% of pupae survived and developed on the flour from the infested mill. None of the larvae survived on any of the other diets.