Microflora Associated with the Confused Flour Beetle, Tribolium Confusum1

Abstract

Larger numbers of bacteria and lesser numbers of storage fungi were isolated from larvae and adults of Tribolium confusum Duv., and the bacteria were more numerous in the insects than in the food from which the insects were taken. These bacteria, when added to autoclaved whole wheat flour, promoted growth and reproduction of T. confusum, but spores of the fungi had little beneficial effect on the insect. Addition of these bacteria to a vitamin-free diet allowed normal development of larvae. In free-choice and olfactometer tests, more adult beetles were attracted to autoclaved flour containing spores of storage fungi, and to autoclaved flour containing bacteria isolated from the insect, than to autoclaved flour alone. The continued presence or increase of T. confusum adults in flour or wheat was always accompanied by a decrease in storage fungi and an increase in bacteria. More adult beetles survived in moldy wheat than inm old-free wheat, at relative humidities of 60% and 75%. Volatile quinones secreted by the adult beetles were relatively toxic to the storage fungi and to some bacteria even when the beetles were not in contact with them. When T. confusum and Sitophilus oryza (L.) were reared together in wheat at a moisture content of 16%–17%, populations of bacteria and storage fungi increased greatly, but with fewer molds than when S. oryza was reared alone.