Confused flour beetles: x-ray and/or malathion modification of population fitness

Data were developed concerning the effects of malathion and X-ray given singly or in combination on the reproductive fitness in populations of Tribolium confusum Jacquelin duVal. Virgin mature beetles sexed as pupae were X-rayed with 0, 1, 2, or 4 kr. From these, 10 pairs were placed on flour media containing various concentrations malathion (0-100 ppm). Culture conditions were 29±2°C and 30–35% relative humidity. Parental mortality and productivity (number of F1 adults) were measured. The minimum lethal dose of malathion for adult T. Confusum was between 10 and 20 ppm. Concentrations less than 10 ppm decreased productivity but did not affect adult mortality during eight-week experimental period. Larval development was retarded by malathion concentrations of 2.5 ppm or greater, with onset of pupation delayed several days. Progressively fewer adults eclosed at 10 and 20 ppm. X-ray doses progressively decreased the reproductive capacity of T. confusum. Exposure to four kr reduced productivity to less than three percent that of control population. Productivity was reduced less by one and 5 ppm malathion than 10 ppm, the latter of which caused extermination of F1 populations by the fourth week. Parental beetles were not killed by 0–10 ppm malathion or 0–4 kR X-ray. The effects from the radiation and malathion combination were more detrimental to the reproductive capacity than were the effects of either stress given singly. An interaction between the malathion and the X-ray effects was obvious, with additive effects noted at all treatments except four kr. The stress from malathion and/or X-ray caused progressive reductions in numbers of almost all F1 populations as dose levels of insecticide and ionizing radiation were increased singly and in combination.