244 



THE TAPEWORMS 



rats and mice from the household and in keeping food out of 

 their reach, and in guarding against the accidental ingestion of 

 such possible intermediate hosts as fleas. 



A closely allied species, H. diminuta (Fig. 91), occurs rarely 

 in man. It closely resembles the dwarf tapeworm but is of 

 larger size (four to 24 inches in length) and has no hooks on the 

 scolex (Fig. 87H). The eggs develop in the larvse or adults of 

 the mealworm, Asopia farinaUs, and in adult beetles, forming 

 cj'sticercoids. When these are eaten by rats, mice or man they 

 transform into adults. In an experiment on man the eggs of 

 the adult worm were found in the faeces 15 days after the eating 

 of an infected mealworm. The larva? of a number of species 

 of fleas also become infected when they ingest the eggs. It is 

 evident that prevention consists in guarding carefully against 

 the accidental swallowing of mealworms with cereals or other 

 foods, and in cautioning children against putting beetles or 



other insects into their mouths. Although 

 the worm is rare in man it is common in 

 rats and mice in many parts of the world, 

 and occurs in nearly all parts of the United 

 States. 



Other Tapeworms (Taeniidae). — A con- 

 siderable number of other tapeworms of this 

 family have been found in man, acciden- 

 tally occurring in him, or having a very 

 limited distribution. 



Of those with limited distribution should 

 be mentioned two species of Davainea. One, 

 D. madagascariensis (Fig. 92), is a small 

 tapeworm reaching a length of ten or twelve 

 inches. It is found, chiefly in children, in many tropical countries, 

 especially in islands and seaports and on ships. The suggestion has 

 been offered that the intermediate host, so far unknown, may be 

 the ubiquitous sea-going cockroach. This tapeworm is interesting 

 in that there is not only a crown of hooks on the head, but there 

 are hooks on the suckers also. The other species of Davainea 

 is D. formosana, recently described by Akashi from children in 

 Formosa and Tokyo. It differs from the preceding species in 

 its larger size, lack of hooks on the suckers, larger size of egg 

 masses in the ripe proglottids and in other minor details. 



B 



Fig. 92. Davainea mad- 

 o{/ascariensi>t; A, head and 

 neck, B, gravid proglottids. 

 X 8. (A, after Blanchard, 

 B, after Daniels.) 



