64 SANITARY ENTOMOLOGY 



are unable to swallow the eggs of the tapeworm. He finds that larval 

 fleas readily swallow the eggs ; these hatch in the intestine of the insect, 

 and the embryos thus released penetrate into the body cavity. They per- 

 sist in the hexacanth stage until the transformation of the flea into the 

 adult, after which they proceed with their development and in a short 

 time reach the cysticercoid stage. Infection of the dog, cat, or human 

 being occurs naturally as a result of swallowing infested fleas. Fleas 

 are exposed to infection owing to the fact that their larvae live in an 

 environment likely to be contaminated by the feces of infested dogs or 

 cats. The eggs of the tapeworm as passed in the feces are grouped in 

 capsules containing about a dozen eggs, so that infection of the insect 

 host is likely to be multiple. The double-pored tapeworm is relatively 

 uncommon in man and most of the cases recorded, of which there have been 

 less than 100 all told, three in the United States, are among young 

 children. Children are more likely than adult human beings to swallow 

 fleas, which would explain the greater frequency of infestation among 

 children. Another possible explanation of the more common occurrence 

 of this parasite among children than among adults is that older persons 

 may possess a greater immunity to infection. Prophylaxis against the 

 double-pored tapeworm consists chiefly in keeping dogs and cats free from 

 lice and fleas, and so far as human beings arc concerned excluding dogs 

 and cats, especially if they are lousy or infested with fleas, from human 

 habitations. 



Hymenolepis diminuta (Rudolphi, 1819) Blanchard, 1891 



Hymenolepis diminuia (the yellow-spotted tapeworm) is of frequent 

 occurrence in the small intestine of rats and mice, particularly the former, 

 and of occasional occurrence in the intestine of man. The adaptability 

 of the adult tapeworm to hosts so widely different as rodents and human 

 beings is paralleled by the adaptability of the larval stage to various 

 intermediate hosts. Cysticercoids belonging to this species have been 

 recorded in various insects, a Lepidopteron, Asopia farinalis, in both 

 larva and imago; a Dermapteron, Anisolabis anmdipes; Coleoptera, AJiis 

 spinosa, Scatirus striatus, and Tenebrio molitor; and fleas CeratophyUus 

 fasciatus, Xenopsylla cheopis, Pulex irritans, and Ctenoceplialus canis; 

 also in myriapods, Fontaria virginiensis and Juhis sp. Nicoll and 

 Minchin (1911) found the cysticercoids in about 4 per cent of the rat 

 fleas (8 out of 207) they examined during a period of thirteen months, 

 and they succeeded in infecting rats with the tapeworm by feeding them 

 fleas, as Grassi and Rovelli (1892) had previously done by feeding other 

 insects. Joj^eux (1916) infected the larvae of Asopia farinalis by feeding 

 the eggs of H. diminuta and believes the cysticercoids recorded in the 



