_Experimental vectors._--Cockroach, U.S.A. (Longfellow, 1913): Recovered from outer part of body and intestinal tract. Family MICROCOCCACEAE * =Micrococcus aurantiacus= (Schroeter) Cohn _Natural vectors._--_Blattella germanica_, U.S.A. (Janssen and Wedberg, 1952). * =Micrococcus citreus= Migula _Natural vectors._--Cockroaches, U.S.A. (Longfellow, 1913). _Experimental vectors._--_Blatta orientalis_, Italy (Cao, 1898). * =Micrococcus epidermidis= (Winslow and Winslow) Hucker _Natural vectors._--_Blattella germanica_, U.S.A. (Janssen and Wedberg, 1952). [cross] =Micrococcus nigrofaciens= Northrup _Source._--Diseased June beetle larvae. _Experimental infection._--_Periplaneta americana_, U.S.A. (Northrup, 1914): Three of four adults were infected by feeding them bread saturated with a broth culture of the _Micrococcus_. After 11 days the tarsi of the cockroaches became infected, and the hind legs split and broke off. Antennae and setae also were affected and micrococci were recovered from the feces. * =Micrococcus pyogenes= var. =albus= (Rosenbach) Schroeter _Natural vectors._--_Blaberus craniifer_, U.S.A. (Wedberg et al., 1949). _Blatta orientalis_, U.S.A. (Tauber, 1940; Tauber and Griffiths, 1942). _Blattella germanica_, U.S.A. (Herms and Nelson, 1913; Herms, 1939; Janssen and Wedberg, 1952). _Experimental vectors._--_Blatta orientalis_, Italy (Cao, 1898); U.S.A. (Tauber and Griffiths, 1942). _Micrococcus pyogenes_ var. _albus_ (=_Staphylococcus albus_) and an unidentified short rod form were found by Tauber (1940) in the hemolymph of _B. orientalis_. These microorganisms were never found together in the same insect and caused loss of appetite, sluggishness, irregular respiratory movements, and paralysis in the cockroach; in the final stages of the disease the legs were folded under the body, the head was tucked beneath the forelegs, the whole insect became arched and maintained this position until death. In some cockroaches infected with the rod pathogen, conjunctival folds, particularly those between the dorsal abdominal sclerites, and the joints of the metathoracic legs ruptured liberating thick white hemolymph filled with bacteria. Tauber suggested that the infection might be spread by contact, especially to newly molted individuals or by actual ingestion of the bacteria by the cockroaches feeding on dead or dying individuals. All the roaches died after successful inoculation with the _Micrococcus_. The bacterial infection was associated with high total hemocyte counts and high percentages of mitotically dividing hemolymph cells (Tauber, 1940); these responses of the insect were interpreted as a mechanism whereby the number of hemocytes increases resulting in an increase in the number of phagocytes for combating the bacteria (Tauber and Griffiths, 1942). * =Micrococcus pyogenes= var. =aureus= (Rosenbach) Zopf _Natural vectors._--_Blaberus craniifer_, U.S.A. (Wedberg et al., 1949).