_Leucophaea maderae_ or _Periplaneta americana_, Philippine Islands (Barber, 1912): From hemolymph. _Periplaneta americana_, U.S.A. (Gier, 1947; Steinhaus, 1959). _Periplaneta australasiae_ and _Periplaneta brunnea_ (Roth and Willis, unpublished data [1954]): In laboratory colonies. Isolated from suspensions of ground insects. In 1954 we received a culture of _Periplaneta brunnea_ from the Department of Public Health, University of Minnesota. These insects began to die off rapidly and the normally lightly pigmented parts of the body became red. Dr. Hillel Levinson, Quartermaster bacteriologist, cultured _Serratia marcescens_ from several moribund individuals. The Department of Public Health of Minnesota had at times in the past cultured _S. marcescens_ but had discarded the cultures and was unaware that it might be surviving in the cockroach colonies (Richards, personal communication, 1954). _Periplaneta_ sp., U.S.A. (Olson _in_ Roth and Willis, 1957a): Isolated from an undetermined species of _Periplaneta_, received in a shipment from the South, a strain of _S. marcescens_ which was toxic to mice when administered intraperitoneally. _Experimental hosts._--_Blaberus craniifer_, U.S.A. (Wedberg et al., 1949): When fed in small numbers, _S. marcescens_ increased to such an extent that the insect's extremities and upper halves of their bodies turned deep red. The insects died after this color appeared and practically pure cultures of _Serratia_ were recovered from the reddened areas. _Blatta orientalis_, Italy (Cao, 1898): Isolated from intestinal contents. Passed unchanged through the gut. _Blattella germanica_, Canada (Heimpel and West, 1959): Not normally pathogenic per os; LD_{50} by injection, is approximately 38,000 bacteria per insect. _Periplaneta americana_, U.S.A. (Gier, 1947): Organism toxic to the cockroach when injected. Cockroaches, U.S.A. (Longfellow, 1913): Isolated from legs and viscera after feeding experiments. * =Shigella alkalescens= (Andrewes) Weldin _Natural vectors._--_Periplaneta americana_, U.S.A. (Bitter and Williams, 1949, 1949a). * =Shigella dysenteriae= (Shiga) Castellani and Chalmers _Experimental vectors._--_Blatta orientalis_, Italy (Spinelli and Reitano, 1932). _Periplaneta americana_, Formosa (Morischita and Tsuchimochi, 1926). _Polyphaga saussurei_, U.S.S.R. (Zmeev _in_ Pavlovskii, 1948). * =Shigella paradysenteriae= (Collins) Weldin _Natural vectors._--_Blatta lateralis_, Tadzhikistan (Zmeev, 1940). _Experimental vectors._--_Periplaneta americana_, Gold Coast Colony (Macfie, 1922). _Polyphaga saussurei_, U.S.S.R. (Zmeev _in_ Pavlovskii, 1948). Cockroaches, Venezuela (Tejera, 1926). Family PARVOBACTERIACEAE =Bacteroides uncatus= Eggerth and Gagnon _Habitat._--Probably intestinal canal of mammals; from human feces. _Natural vectors._--_Blatta orientalis_, Poland (Nicewicz et al., 1946): From intestinal canal. * =Brucella abortus= (Schmidt and Weis) Meyer and Shaw