William R. Kellen

Bacillus sphaericus Neide as a pathogen of mosquitoes.

Abstract A strain of Bacillus sphaericus Neide was isolated from moribund fourth-instar larvae of Culiseta incidens (Thomson) collected near Fresno, California. The bacterium is a gram-variable, aerobic sporeformer and is facultatively parasitic to mosquitoes in laboratory tests. It invades larvae via the alimentary canal and is capable of producing fatal septicemias. First detectable signs of infection, loss of normal turgor and motility, occurred after 3 days of exposure to bacilli. As the infection progressed, the afflicted larva became dark brown in color, and frequently died remaining attached to the water surface. Tests were performed with larvae of 10 species of mosquitoes; all were susceptible to the bacterium.