Rearing Stored-Product Insects for Laboratory Studies: Bean and Cowpea Weevils12

Abstract

A standardized system was developed for routine weekly maintenance of minimum stocks of bean weevils. Acanthoscelides obtectus (Say), on Red Kidney beans, phaseolus vulgaris L., and cowpea weevils, Callosobruchus maculates (F.), on blackeye peas, Vigna sinensis (Torner) Savi. All cultures were contained in quart jars at a constant room temperature of 80±2°F and 55±5% relative humidity. Regular use of CO2 anesthesia facilitated frequent handling of cultures and had no deleterious effect on yield. Parent weevils were collected on the day of peak emergence from cultures which had been screened to assure collection of adults within the desired age range. Each week 1 culture of cowpea weevils was started by placing 300 unsexed parents, ranging from recently emerged to 2 days old, on I pint of blackeye peas. Each culture yielded an average of 6400 progeny. Emergence began in 22 days, reached its peak at 28 days, and continued in usable numbers of insects through the 35th day after initial introduction of parent stock. Bean weevil cultures were set up by placing 150 adults, ranging from recently emerged to 3 days old, on I V2 pints of Red Kidney beans. Each culture was expected to yield approximately 2200 progeny, based on test results in which an average production of 1500 per pint of beans was obtained with 100 parents. Emergence of adults began on the 29th day, reached its peak on the 33rd day, and continued in usable numbers through the 38th day following introduction of parents. Three cultures of bean weevils were started each week. To obtain comparable numbers of insects, the ratio of 1 cowpea to 3 bean weevil cultures was maintained when the number of cultures was increased to provide insects for scheduled experiments. Cultures were increased in number by screening to remove adults soon after first emergence was observed; parent weevils of a known age were collected at regular intervals thereafter to start new cultures.