Geopetitia aspiculata was found in 12 species of Passeriformes, one species of Cor-aciiformes, and one species of Charadriiformes which died in a free-flight area in the Tropical House at the Assiniboine Park Zoo, Winnipeg, Canada. The nematodes occurred in chronic inflammatory cysts attached to the serosa of the posterior end of the esophagus, proventriculus, and the anterior part of the gizzard. Posterior ends of worms were observed to extend from the cyst into the lumen of the proventriculus. Birds hatched and raised in the Tropical House acquired infections, probably through the agency of feral crickets. Experimental studies showed that G. aspiculata developed to the infective third stage in the fat body of Acheta domesticus (L). This is the first transmission cycle of Geopetitia spp. to be elucidated and the egg, first, third, and early fifth stages of the parasite are described. The absence of spicules in males of G. aspiculata is confirmed. Geopetitia aspiculata was probably introduced to the Zoo by infected tropical birds obtained from dealers or other zoos. The wild source of the parasite is not known since G. aspiculata has never been reported in wild birds; the report of G. aspiculata in wild Piciformes in Cuba by Barus (1971) is in error.