60 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



that the closer the association between any insect and man the 

 greater will be the likelihood of disease transmission, provided 

 the other necessary conditions are fulfilled. Domesticity, there- 

 fore, is a condition which affects profoundly the phenomenon of 

 disease transmission, and the importance of vectors in many 

 cases at least will depend upon the degree to which their domes- 

 ticity has been developed. 



There is, however, a class of diseases, which is likely to become 

 extended with future study, in which domesticity does not act 

 as an important factor. Such diseases as spotted fever and 

 tsutsugamushi are examples. The essential condition in such 

 cases seems to be a natural contact with the reservoir of the 

 disease, and accidental contact with man. The spotted fever 

 tick is in no sense a domestic species. In fact, it is quite the 

 reverse. 1 It decreases in numbers with the advent of man and 

 with his operations in the fields. The tick probably acquires 

 the virus of spotted fever from certain wild animals. A tick 

 infected in this way happens to attach itself to man as it would 

 to any other animal. The attachment is, therefore, to be looked 

 upon as more or less an accident which is of importance by rea- 

 son of the fact that it establishes a connection between man and 

 the virus. Likewise tsutsugamushi fever has its reservoir in 

 wild rodents and reaches man through the intervention of a mite, 

 Trombidium akamushi, which attacks him when he goes into the 

 fields. 2 



There are no very definitely established cases at present but 

 it is likely that there will be found to be another class of diseases 

 in which insects are of importance, where the essential condi- 

 tion is accidental contact with the pathogenic organism (instead 

 of natural contact as in the -case of spotted fever) , and accidental 

 contact with food. If cockroaches become definitely connected 

 with tuberculosis, or similar maladies, as seems likely to be the 

 case, they will present such a class as we believe will ultimately 

 be found to be important. 3 Of course the importance of this 

 mode of transference will be profoundly affected by such condi- 

 tions as the abundance of the insects, and the viability of the 

 pathogenic organisms. 



Another class of cases is that of diseases which may be trans- 

 mitted by insects which become contaminated by feeding upon 

 or visiting the body discharges of invalids. An example of this 

 is a species of Oscinis which seems to have developed a rather 



1 Hunter, W. D. and F. C. Bishopp. Bulletin 105, Bureau of Entomology, 

 U. S. Department of Agriculture. 



2 Ashburn and Craig. Philippine Journal of Science, B. Ill, p. 1. 



3 Barber, M. A. Philippine Journal of Science, B. IV, p. 4. 



