RELATION OF INSECTS TO THE PARASITIC WORMS 57 



Prophylaxis in the case of this tapeworm is obviously largely 

 dependent upon fly control measures. 



Other Tapeworms 



According to Villot (1883) the larval tapeworm observed by Stein 

 (1852) in the larva of Tenebrio molitor belongs to the tapeworm of the 

 mouse, known as Hymenolepis microstoma. The same writer (1878, 

 1883) also associates with certain tapewonns of shrews, two species of 

 larval tapeworms which he found in myriapods, Glomeris limhata. Fur- 

 ther investigations of these parasites appear necessary to substantiate 

 the views held by Villot as to their specific identity. Ackert (1918, 1919) 

 has recently recorded some experiments in which chickens were given 

 house flies and became infested with tapeworms (Davainea cesticUlus and 

 D. tetragona). The immature stages of these parasites were not, how- 

 ever, seen in the flies and the possibility is not excluded that the chickens 

 became infected from some source other than the flies, notwithstanding 

 the precautions taken against extraneous infection. Guberlet (1919) 

 caught stable flies (Stomoxys calcitrans) in poultry yards where the 

 chickens were commonly infested with Hymenolepis carioca (Magalhaes, 

 1898) and fed them to young chicks with the result that some of them 

 became infested with this tapeworm. He concludes that the stable fly 

 possibl}' serves as an intermediate host of this tapeworm. 



TREMATODA OR FLUKES 



All species of flukes whose life history is known depend upon molluscs 

 as hosts for certain larval stages, and they may or may not require one 

 or more additional intermediate hosts before they reach the definitive host. 

 It is as intermediate hosts following the first intermediate host, a mollusc, 

 that insects can play a part in the propagation of flukes. As yet it has 

 not been shown that insects are concerned in the life history of any of 

 the flukes (about 100 known species) that aff*ect human beings or domestic 

 animals, but as the life history of all of these parasites has not been 

 determined it is quite likely that in the case of some species insects will be 

 found to act as intermediate hosts. Different species and groups of 

 species show various types of life history with reference to the number 

 of larval stages through which the parasite passes and the number of 

 intermediate hosts required. A comparatively simple life cycle is as 

 follows : The mature fluke in the definitive host produces eggs which pass 

 to the exterior in the feces. Under suitable conditions of moisture and 

 temperature the Qgg hatches and a ciliated larva, the miracidium, issues. 

 If this miracidium finds a suitable mollusc (diff'erent species of molluscs 



