CESTODE INFECTION IN CHICKENS 235 



These six birds were kept together in a cage and were fed on 

 corn meal and bread crumbs. The three birds that were fed flies 

 were caught and the insects were given to them from the hand. 



A number of stable flies (Stomoxijs calcitrans)-weve used in 

 the experiments with this species of worm, but they would not live 

 under experimental conditions for any length of time. They would 

 usually die within 24 to 36 hours, except in one case when six lived 

 for five days. They were sectioned, but nothing could be found. 



On numerous occasions I have observed maggots in the drop- 

 pings beneath the chicken roosts. Now, since house-flies are in the 

 habit of breeding in such places, it seemed possible that infection 

 might take place in the maggot stage of the flies. Experiments 

 were then tried with the maggots of Musca domestica and Stomoxys 

 calcitrans. Thirty Musca domestica maggots were fed on segments 

 of three species of cestodes, Davainea cesticillus, Davainea tetra- 

 gona, and Choanotaenia infimdihuliformis. The maggots devel- 

 oped puparia in a day or two. Some were sectioned in the pupa 

 stage. The rest developed into adults and were sectioned, a few 

 were dissected, but only negative results were obtained. Fifty 

 maggots of Stomoxys calcitrans were fed on proglottids of the same 

 three species of tapeworms. The maggots went into the pupal stage 

 within two or three days. Some were sectioned in the pupal stage. 

 Most of them developed into adults and were sectioned while a few 

 were dissected. No positive results were obtained from either pupal 

 or adult stages. 



From the foregoing it seems probable that flies are not the 

 intermediate hosts for Davainea cesticillus and Davainea tetragona, 

 as the experiments that I have carried on with them are extensive 

 enough to appear conclusive. However, the small number of vari- 

 eties of insects present in the locality seems to throw the burden 

 upon the flies, since they were so abundant and observations show 

 that they are taken and eaten by the chickens that are most heavily 

 infested. The adult birds eat all other insects that are easy to 

 catch, but since the flies are more difficult to take as prey they 

 leave them alone. If the infection is direct, the adults would have 

 fully as much chance as the young birds because they get food and 

 water together and have the same environment. 



In the case of Choanotaenia infundibuliformis it seems to be 

 clear that the house-fly is the intermediate host. Grassi and 

 Rovelli hold that it is the intermediate host on a purely structural 

 basis. My experiments show that it is certainly an intermediate 



