102 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
Disease.—Parasites in the walls of the esophagus, tongue, and 
forestomach of the definitive hosts. 
Natural intermediate hosts —Blatta orientalis, Netherlands, Avie 
dam (Baylis, 1925): About one in seven cockroaches (Periplaneta 
americana and B, orientalis) contained larvae. 
Blattella germamica, U.S.A., Minnesota (Hitchcock and Bell, 1952). 
Periplaneta americana, Denmark and Saint Croix (Fibiger, 1913, 
1913a; Fibiger and Ditlevsen, 1914). Netherlands, Amsterdam (Bay- 
lis, 1925). About one in seven cockroaches (P. americana and Blatta 
orientalis) was found to contain the parasite larvae. Surinam (Baylis, 
1925). Argentina (Bacigalupo, 1930). England (Leiper, 1926). 
South Africa (Porter, 1930). U.S.A., Minnesota (Hitchcock and 
Bell, 1952) : Several hundred cockroaches (P. americana and Blattella 
germanica) were caught at a rendering plant; 90 percent of these con- 
tained encysted larvae. Formosa (Yokagawa, 1924, 1925, 1925a) : 
Cockroaches (P. americana and P. australasiae) in the vicinity of 
Taihoku were about 30 percent parasitized. 
Periplaneta australasiae, Formosa (Yokagawa, 1924, 1925, 1925a). 
Experimental intermediate hosts—Blattella germanica, Denmark 
(Fibiger and Ditlevsen, 1914). U.S.A., Minnesota (Hitchcock and 
Bell, 1952). France (Brumpt, 1949). 
Blatta orientalis, Denmark (Fibiger and Ditlevsen, 1914). 
Periplaneta americana, Denmark and St. Croix (Fibiger, 1913; 
Fibiger and Ditlevsen, 1914). U.S.A., Minnesota (Hitchcock and 
Bell; 1952). 
Development in intermediate host-——-The cockroach becomes in- 
fected by feeding on rat feces containing embryonated eggs (pl. 7, 
right) of the worm. The hatched larvae migrate through the diges- 
tive tract and encyst in the muscles of the thorax and legs. The in- 
fected cockroaches are then capable of infecting rats (Fibiger and 
Ditlevsen, 1914). 
Definitive hosts—Wild rats (Rattus norvegicus and Rattus rattus), 
and in laboratory rats, white mice, rabbits, and guinea pigs (Fibiger 
and Ditlevsen, 1914). 
Development in definitive host.—The rat becomes infected by eating 
cockroaches containing encysted nematode larvae (pl. 7, left). The 
nematode larvae leave the cyst and enter the squamous-celled epi- 
thelium of the fundus of the stomach and also the epithelium of the 
esophagus, tongue, and mouth. After about 2 months, the female 
worms lay eggs which are voided with the rat feces (Fibiger and 
Ditlevsen, 1914). 
