DISEASE OF THE LARVAE OF TENT CATERPILLARS CAUSED BY A SPOREFORMING BACTERIUM

Abstract

A newly discovered bacterial disease of larvae of Malacosoma pluviale (Dyar) (Lep.) is caused by infection of the gut with a large, motile, sporeforming bacterium, Bacillus sp., that increases in size before sporulation and bears the spore without bulging. It has not been cultivated. The bacterium invades the host with the food and multiplies in the midgut and foregut, producing changes in the pH and causing dysentery in the host. Sporulation occurs in the gut and both rods and spores are passed in the faeces and spread the disease. The infected larva loses its appetite, regurgitates excessively, produces wet faeces, decreases markedly in length, and dies in a characteristic, short, dry, mummified condition after about a week. Small ingested doses of spores initiate infection in laboratory populations of M. pluviale in all instars. M. americana (F.) also is susceptible to the disease but M. disstria Hbn. is resistant, only a few individuals dying from it.