In Formosa, _Tetrastichus hagenowii_ was an important parasite of cockroach eggs (Maki, 1937). Sonan (1924) reported 30 percent parasitization of 65 oöthecae of _Periplaneta americana_ and _P. australasiae_ collected in Formosa. In Bangalore, India, the natural parasitization of randomly collected oöthecae of _P. americana_ varied from 21 percent (of 495 oöthecae), July 1947-June 1948, and 43 percent (of 288 oöthecae), July-December 1948, to 57 percent (of 178 oöthecae), July-October 1949 (Usman, 1949). Cameron (1955) obtained _T. hagenowii_ from oöthecae collected in Trinidad, B.W.I., and Saudi Arabia; some 15 percent of the oöthecae of _P. americana_ and _P. australasiae_ collected in October in Trinidad were parasitized; a later collection (March) was 34 percent parasitized; a small sample of _P. americana_ oöthecae was 65 percent parasitized. The oöthecae collected in Saudi Arabia in March were 20 percent parasitized. Plank (1947) found that the eggs of the American cockroach in Puerto Rico (probably in laboratory cultures) were so heavily parasitized by _T. hagenowii_ that he had to use _P. australasiae_ for experimental purposes; in 1950 Plank stated that more than 50 percent of American cockroach oöthecae were parasitized. Fahringer (1922) stated that _Prosevania punctata_ could be used to eradicate cockroaches, but he did not test his hypothesis. Marlatt (1902) felt that the usefulness of _Evania appendigaster_ in biological control was impaired by _Tetrastichus_ acting as a hyperparasite (see footnote 6, p. 236). However, Wolcott (1951) stated that in Puerto Rico _E. appendigaster_ is quite abundant and is a factor of considerable importance in controlling cockroaches. Kadocsa (1921) stated that _Brachygaster minutus_ and _Evania appendigaster_ were not important in the biological control of cockroaches. These general statements are not supported by experimental evidence. It is likely that the smaller wasp egg parasites are more effective than the evaniids in controlling cockroaches. Only one evaniid develops in a parasitized oötheca, but many individuals of the other wasps develop in one oötheca and the number of females that emerge is usually large. However, Cameron (1957) concluded that, with a parasitism rate of 25 to 29 percent and three to four generations a year, against one or less for the host, _Evania appendigaster_ in the areas where it is established is a valuable control agent.