* =Mycobacterium= spp. _Natural vectors._--_Periplaneta americana_, U.S.A. (Leibovitz, 1951; Micks _in_ Roth and Willis, 1957a). Family ACTINOMYCETACEAE * =Nocardia= sp.? _Natural vectors._--_Periplaneta americana_, U.S.A. (Leibovitz, 1951). Family STREPTOMYCETACEAE =Streptomyces leidynematis= Hoffman _Habitat._--Surface of the nematodes _Hammerschmidtiella diesingi_ and _Leidynema appendiculata_ in _Periplaneta americana_, U.S.A. (Hoffman, 1952, 1953): Eighteen percent of 192 nematodes found in 52 adult cockroaches were infected with the bacterium. Order CARYOPHANALES Family ARTHROMITACEAE =Arthromitus intestinalis= (Valentin) Peshkoff _Synonymy._--_Hygrocrocis intestinalis._ _Habitat._--_Blatta orientalis_, Europe (Valentin, 1836; Robin, 1847, 1853; Peshkoff, 1940): Isolated from intestinal tract. The organism appears as fragments in fecal masses or as fibers adhering to the mucous membrane of the large intestine (Robin, 1853). Cockroach, France? (Chatton and Pérard, 1913). Order SPIROCHAETALES Family SPIROCHAETACEAE [cross] =Spirochaeta blattae= Tejera _Habitat._--_Blaberus atropos_, Venezuela (Tejera, 1926): Isolated from intestinal tract. * [cross] =Spirochaeta periplanetae= Laveran and Franchini _Habitat._--_Blatta orientalis_, France (Laveran and Franchini, 1920a). Cockroaches, Venezuela (Tejera, 1926): Tejera reported finding "_Spirochaeta blatarum_ Laveran et Franchini" which may have been a lapsus. Family TREPONEMATACEAE [cross] =Treponema parvum= Dobell _Habitat._--_Blatta orientalis_, England (Dobell, 1912); U.S.S.R.? Zasukhin (1930): From intestinal tract. [cross] =Treponema stylopygae= Dobell _Synonymy._--_Spirochaeta stylopygae_ Zuelzer. _Habitat._--_Blatta orientalis_, England (Dobell, 1912); U.S.S.R.? Zasukhin (1930): From intestinal tract. =Unidentified spirochaetes= _Habitat._--_Blatta orientalis_, U.S.S.R. (Yakimov and Miller, 1922): Spirochaetes and spirilla were found in the intestines of 70 percent of 124 specimens collected in Petrograd. _Periplaneta americana_, Gold Coast Colony (Macfie, 1922). ADDITIONAL BACTERIA WHOSE TAXONOMIC POSITION IS UNKNOWN * "=B. aerobio del pseudoedema maligno=" of Cao _Natural vectors._--_Blatta orientalis_, Italy (Cao, 1906). =B. alcaligenes beckeri= _Natural vectors._--_Blatta orientalis_, Poland (Nicewicz et al., 1946): Isolated from intestinal tract. * "=B. del pseudoedema maligno=" of Cao _Natural vectors._--_Blatta orientalis_, Italy (Cao, 1906). * "=Bacillo proteisimile=" of Cao _Natural and experimental vectors._--_Blatta orientalis_, Italy (Cao, 1898, 1906). * "=Bacillo del barbone dei bufali=" of Cao _Experimental vectors._--_Blatta orientalis_, Italy (Cao, 1898). * "=Bacillo similcarbonchio=" of Cao _Natural and experimental vectors._--_Blatta orientalis_, Italy (Cao, 1898, 1906). * "=Bacillo similtifo=" or "=Bacillo tifosimile=" of Cao