_Natural vectors._--_Periplaneta americana_, U.S.A. (Eads et al., 1954). * =Salmonella typhimurium= (Loeffler) Castellani and Chalmers _Natural vectors._--_Blattella germanica_, Belgium (Graffar and Mertens, 1950). _Nauphoeta cinerea_, Australia (Mackerras and Mackerras, 1948). _Experimental vectors._--_Blaberus craniifer_, U.S.A. (Wedberg et al., 1949). _Blatta orientalis_, U.S.S.R. (Rozengolts and Ȋȗdina _in_ Pavlovskii, 1948). _Blattella germanica_, Belgium (Graffar and Mertens, 1950); U.S.A. (Olson and Rueger, 1950; Janssen and Wedberg, 1952; Beck and Coffee, 1943); U.S.S.R. (Rozengolts and Ȋȗdina _in_ Pavlovskii, 1948). _Nauphoeta cinerea_, Australia (Mackerras and Pope, 1948). _Periplaneta americana_, U.S.A. (Beck and Coffee, 1943; Jung and Shaffer, 1952). _Periplaneta australasiae_ and _Supella supellectilium_, Australia (Mackerras and Pope, 1948). _Polyphaga saussurei_, U.S.S.R. (Zmeev _in_ Pavlovskii, 1948). * =Salmonella typhosa= (Zopf) White _Natural vectors._--_Blatta orientalis_, Italy (Antonelli, 1930, 1943). _Experimental vectors._--_Blaberus craniifer_, U.S.A. (Wedberg et al., 1949). _Blatta orientalis_, Italy (Spinelli and Reitano, 1932); U.S.A. (McBurney and Davis, 1930); U.S.S.R. (Rozengolts and Ȋȗdina _in_ Pavlovskii, 1948). _Blattella germanica_, U.S.A. (Janssen and Wedberg, 1952); Germany (Jettmar, 1927); U.S.S.R. (Rozengolts and Ȋȗdina _in_ Pavlovskii, 1948). _Periplaneta americana_, Gold Coast Colony (Macfie, 1922); Netherlands (Akkerman, 1933); Formosa (Morischita and Tsuchimochi, 1926); U.S.A. (Olson _in_ Roth and Willis, 1957a). _Periplaneta australasiae_, Formosa (Morischita and Tsuchimochi, 1926). _Polyphaga saussurei_, U.S.S.R. (Zmeev _in_ Pavlovskii, 1948). Cockroaches [presumably _Blatta orientalis_, _Blattella germanica_, and/or _Periplaneta americana_], Egypt (El-Kholy and Gohar, 1945). =Serratia marcescens= Bizio _Synonymy._--_Bacillus prodigiosus_, _Bacterium prodigiosum_. _Habitat._--Water, soil, milk, foods, and various insects. _Natural hosts._--_Blatta orientalis_, Poland (Nicewicz et al., 1946): From intestinal tract. Italy (Spinelli and Reitano, 1932). _Blattella germanica_, Canada (Heimpel and West, 1959). _Diploptera punctata_, _Nauphoeta cinerea_, _Neostylopyga rhombifolia_, _Panchlora nivea_, _Pycnoscelus surinamensis_, and _Supella supellectilium_, U.S.A. (Roth and Willis, unpublished data, 1958): The organism was isolated and identified by Dr. Hillel Levinson, Quartermaster bacteriologist, from dead specimens found in our laboratory colonies which showed the red coloration characteristic of insects that have died with infections of _S. marcescens_ (pl. 16, A, B). _Leucophaea maderae_, U.S.A. (Levinson, personal communication, 1958): The organism was isolated from the hemolymph of living insects while attempting to determine the cause of unexplained mortality in our laboratory colony of this insect.