RELATION OF INSECTS TO THE PARASITIC WORMS 61 



of the esophagus ; and after fifteen days they had sunk themselves into 

 the wall of the esophagus and had developed still further. Grassi con- 

 cluded that cockroaches act as intermediate hosts, swallowing the eggs in 

 the feces of infested dogs, and'in turn being swallowed by dogs, Seurat 

 (1913), however, believes that Grassi was mistaken as to the identity of 

 the encysted nematodes found in the cockroaches, and that they were 

 really the larvas of Spirura gastrophila, the adult of which occurs in the 

 stomach of the cat, hedgehog (Ermaceus algirus), and fox (Vvlpes wipes 

 atlantica). Seurat (1912, 1916) finds what he considers to be the larvae 

 of S. scmguinolenta encysted in a great variety of animals including 

 beetles, reptiles, birds, and mammals. The presence of the encapsulated 

 larvas in various vertebrates he explains as the result of the ingestion of 

 insects infested with the larvse. If the vertebrate is not a host in 

 which the parasites can continue their development as they would in 

 their normal host the dog, they migrate into the wall of the alimentarj' 

 tract or mesentery and become reencysted without further development. 

 If, however, the infested insect is swallowed by a dog the larvae, after 

 they have been freed by digestion of the cysts surrounding them, continue 

 their development and finally reach maturity. Seurat in fact found 

 that encysted larvae in insects identified as those of S. sanguinolenta when 

 fed to mice became reencysted in the manner described. Seurat (1916) 

 records the following insects as hosts of the larvas of S. sanguinolenta, all 

 of them beetles: Scardba:us (Ateuchus) sacer, vScarabceus (Ateuchetus) 

 variolostbs, AJcis goryi, Geotrupes douei, Copris hispanus, and Gymno- 

 pleurus sturmi. According to Seurat the life cj'cle of S. sanguinolenta 

 would be as follows: The eggs pass out of .nfested dogs in the feces, 

 are ingested by beetles, hatch, and the larvae after a period of growth and 

 development become encysted. If infested insects are swallowed by dogs 

 or wolves the larval worms are released from their capsules and develop to 

 maturity. If the insects are swallowed by other animals, the larvae may 

 become freed from their cysts as in the alimentary tract of the dog, 

 but they are unable to develop further and leave the lumen of the 

 alimentary tract and become reencysted in the tissues to which they 

 migrate. In such a case, of course, there is a possibility of their resuming 

 their development if the infested animal should afterwards be devoured by 

 a dog or a wolf, but this possibility apparently has not yet been sub- 

 stantiated. 



Spirura gastropUla (Mueller, 1894) Marotel, 1912 



This nematode in the adult stage occurs in the stomach and the lower 

 end of the esophagus of the cat. It has also been recorded by Seurat 

 (1913) from the stomach of a hedgehog (Erinaceus algirus) and the 

 stomach and esophagus of a fox (Vvlpes vvlpes atlantica), and by the 



