At the time of oviposition the nematode eggs are in the very earliest stages of cleavage. In 36 hours a motile, tadpole-like stage is reached and in a few days the embryo becomes quiescent and nonmotile. This nonmotile stage is infective whereas the motile embryonic stage is not. Feeding experiments proved that transmission of the nematode is direct. The worm reaches sexual maturity in 20 or 30 days after being ingested by the cockroach (Dobrovolny, 1933). The bacterium _Streptomyces leidynematis_ Hoffman grows on the cuticle of _H. diesingi_ (Hoffman, 1953). The bacterium apparently is only anchored to the nematode and probably obtains its food from the intestinal contents of the cockroach. See notes under _Leidynema appendiculata_. =Hammerschmidtiella neyrai= Serrano Sánchez, 1945 _Synonymy._--_Hammerschmidtiella neyrae_ Serrano Sánchez, 1947. [According to M. B. Chitwood, personal communication, 1957, Serrano Sánchez's emendation is apparently an error.] _Natural host._--_Blatta orientalis_, Spain, Grenada (Serrano Sánchez, 1947): Of 2,943 specimens examined, 1,143 were parasitized by oxyurids and of these 45 percent contained _H. neyrai_. =Leidynema appendiculata= (Leidy, 1850) Chitwood, 1932 _Synonymy._--_Oxyuris blattae orientalis_ Hammerschmidt, 1847, of Bütschli, 1871, and _Oxyuris blattae-orientalis_ of Magalhães, 1900; _Oxyuris blattae_ Hammerschmidt, 1847, of Galeb, 1878; _Aorurus_ (_Thelastoma_) _appendiculatus_ Leidy, 1850. [Chitwood, 1932.] Serrano Sánchez (1947) has divided this species into three geographical varieties as follows: _L. appendiculata_ (Leidy, 1852) (Dobrovolny and Ackert, 1934) var. _indiana_; _L. appendiculata_ (Leidy, 1852) (Chitwood, 1932) var. _americana_; _L. appendiculata_ (Serrano Sánchez, 1947) var. _hispana_. However, Basir (1956) does not recognize these varieties. The Russians recognize _hispana_ (M. B. Chitwood, personal communication, 1957). _Natural hosts._--_Blaberus atropos_, South America (Chitwood, 1932). _Blatta orientalis_, Egypt? (Galeb, 1878); Europe (Bütschli, 1871); U.S.S.R. (Sobolev, 1937; Sondak, 1935); U.S.A., Nebraska (Todd, 1944); Spain (Serrano Sánchez, 1947): Recorded as var. _hispana_. Czechoslovakia (Groschaft, 1956). England (Lee, 1958a). _Blatta orientalis_ or _Periplaneta americana_, Brazil (Magalhães, 1900). _Periplaneta americana_, U.S.A.: Texas (Todd, 1943); Nebraska (Todd, 1944); Kansas (Dobrovolny, 1933; Dobrovolny and Ackert, 1934); North Carolina (Hatcher, 1939); Iowa, North Dakota, Michigan (Hoffman, 1953). Czechoslovakia (Groschaft, 1956). England (Lee, 1958a). Cockroach, Venezuela (Tejera, 1926). Cockroaches (_Blatta orientalis_, _Blattella germanica_, and/or _Periplaneta americana_), U.S.A. (McAdow, 1931). Chitwood (1932) also listed China for distribution of the worm, but we could not tell which host was involved.