Infectivity tests were conducted with several species ofBacillusand a fungus,Beauveria bassiana(Balsamo) Vuillemin, againstFannia canicularis(L.) andF. femoralis(Stein). Results of qualitative tests with bacteria were variable, and relatively few of the isolates were capable of producing moderate (40–60%) levels of mortality against larvae ofF. canicularis,which was the most susceptible of the host species. The most effective bacterium, causing 67% kill, was an unidentified variety ofB. thuringiensisBerliner. The NRRL A-6511 strain ofB. bassianaproduced higher levels of mortality against larvae of both species of host than the comparative bacteria, and caused up to 87% kill ofF. femoralislarvae after 3 successive passages through susceptible hosts.