OF WASHINGTON, VOLUME XVII, 1915 61 



special habit of visiting the external lesions of yaws. 1 It has 

 been noticed that this insect will be found in considerable num- 

 bers on the lesions of patients in hospitals as soon as the bandages 

 have been removed. Of course the house fly is the most con- 

 spicuous example of an insect which may be concerned in the 

 transmission of diseases in this manner. 



The last class of cases consists of those in which insects serve 

 as intermediate hosts for cestode or nematode parasites. The 

 parasitism of the hog by Echinorhynchus hirudinaceus is especially 

 interesting because the insect concerned belongs to the order 

 Coleoptera which is not generally associated with disease organ- 

 isms. The necessary host for one stage of this parasite is the 

 larva of some scarabseid beetle. In Europe the species of Melo- 

 lontha and in this country species of Lachnosterna are involved. 2 

 The infestation of the swine is rather general and sometimes of 

 grave importance on account of perforations and for other reasons. 

 Occasional human cases are also recorded. This is another case in 

 which the destruction of the insect intermediate host would result 

 in the control of the disease. It is rather novel, however, because 

 the destruction of white grubs is undertaken on account of the 

 injury they do the crops, while ordinarily the destruction of 

 intermediate insect host must be predicated upon the fact of 

 disease transmission or the fact of direct annoyance to man. A 

 similar instance is found in a tape worm of the dog (Dyphylidium 

 caninum). In this case some insect is necessary for the develop- 

 ment of the cysticercus stage of the parasite. 3 Usually it is a 

 flea or louse which forms this function. As in the other case 

 man is directly concerned to at least a certain extent, since 

 Blanchard summarized not less than sixty cases which has been 

 recorded in man up to 1907. 



Among the strictly human cestode parasites, one of the most 

 important is Hymenolepsis diminuta. In this case the necessary 

 intermediate host for the cysticercus stage may be any one of 

 several insects. This has been proven in species of the follow- 

 ing genera Pyralis, Anisolabis, Ascis and Scaunts* Thus cer- 

 tain common household insects, like the flour moth, have rela- 

 tion to man which is frequently overlooked. 



In this discussion we have purposely omitted the attack of 

 insects against man in purely mechanical ways, such as myiasis, 

 and have restricted ourselves to the cases in which the injury is 

 not direct but indirect through infection by specific organisms. 



1 Xicholls, L. Bulletin Entomological Research, III, No. 14, 199. 



2 Ransom, B. H. Yearbook, U. S. Dept. Agriculture, 1905, 155. 



3 Castellani, A., and A. .1. Chalmers. Manual of Tropical Medicine, 1913, 

 502. 



4 Id., 503. 



