ENTOMOLOGY

RELATION OF INSECTS TO THE PARASITIC WORMS 61of the esophagus; and after fifteen days they had sunk themselves intothe wall of the esophagus and had developed still further. Grassi concludedthat cockroaches act as intermediate hosts, swallowing the eggs inthe feces of infested dogs, and·in turn being swallowed by dogs. Seurat(1918), however, believes that Grassi was mistaken as to the identity ofthe encysted nematodes found in the cockroaches, and that they werereally the larvre of Spirora gaatrophila, the adult of which occurs in thestomach of the cat, hedgehog (Erinaceus algiro8), and fox (Vu.lpe8 vUlpesatlantica). Seurat (191~, 1916) finds what he considers to be the llltrvreof S. 8anguinolenta encysted in a great variety of animals includingbeetles, reptiles, birds, and mammals. T4e presence of the encapsulatedlarvre in various vertebrates he explains as the result of the ingestion ofinsects infested with the larvre. If the vertebrate is not a host inwhich the parasites can continue their development as they would intheir normal host the dog, they migrate into the wall of the alimentarytract or mesentery and become reencysted without further development.If, however, the infested insect is swallowed by a dog the larvre, afterthey have been freed by digestion of the cysts surrounding them, continuetheir development and finally reach maturity. Seurat in fact foundthat encysted larvre in insects identified as those of S. aanguinolenta whenfed to mice became reencysted in the manner described. Seurat (1916)records the following insects as hosts of the larvre of S. aanguinolenta, allof them beetles: Scarabo:ua (Ateuchus) aacer, .scarabo:ua (Ateuchetua)varioloaua, Aki8 gorlli, Geotropes douei, Cop ria hispanus, and GlImnopleurossturmi. According to Seurat the life cycle of S. sallgl£inolenta,vould be as follows: The eggs pass out of .nfested dogs in the feces,are ingested by beetles, hatch, and the larvre after a period of growth anddeVelopment become encysted. If infested insects are swallowed by dogsor wolves the larval worms are released from their capsules and develop tomaturity. If the insects are swallowed by other animals, the larvre maybecome freed from their cysts as in the alimentary tract of the dog,but they are unable to develop further and leave the lumen of thealimentary tract and become reencysted in the tissues to which theymigrate. In such a case, of course, there is a possibility of their resumingtheir development if the infested animal should afterwards be devoured bya dog or a wolf, but this possibility apparently has not yet been substantiated.Spirora gaatrophila (Mueller,OS94) Marotel, 191~This nematode in the adult stage occurs in the stomach and the lowercnd of the esophagus of the cat. It has also been recorded by Seurat(1918) from the stomach of a hedgehog (Erinaceu8 algiros) and thestomach and esophagus of a fox (Vulpe8 vUlpe8 atlantica), and by the