86 INFECTION AND IMMUNITY. 



many of the female mosquitoes die in the water 

 after they have laid their eggs and that the water 

 thus becomes contaminated with the filaria. The 

 use of such water results in the infection of man 

 through his intestinal tract. Suspicion falls on 

 several species of mosquitoes: Culex pipiens, C. 

 ciliaris, C. fatigans; Anopheles costtilis, A. rossi, 

 A. maculipennis. 



A number of worms which are parasitic in one 

 animal or another are derived from insects, the 

 latter serving as hosts for the larval stages. Infec- 

 tion of the digestive canal originates after eating 

 the insects (See Nuttall, Hygienische Eundschau, 

 1899, ix, 505). 



specificity in There is a certain degree of specificity in the 

 Transmission, transmission of a disease by an insect, but this is 

 by no means absolute. In yellow fever it appears 

 to be very strong, inasmuch as only one species of 

 mosquito appears to be capable of carrying the 

 disease (Stegomym fasciata). An opposite ex- 

 treme is found in the case of malaria, in which at 

 least twenty-five different species of Anopheles 

 have been shown to be capable of either natural or 

 experimental transmission. 14 Several species of 

 ticks are able to carry Texas fever and probably 

 other piroplasmoses of cattle. At least two spe- 

 cies of ticks carry Eocky Mountain spotted fever 

 (Dermacentor venustus, Banks, and D. modestus, 

 Banks). Two species of tsetse flies may carry the 

 parasites of either nagana or sleeping-sickness. 

 The carrying power, however, is usually limited 

 to different species under a common genus. As far 

 as observations have gone only Anopheles carry 



14. Ruge : Kolle and Wassermann's Handbuch d. path. 

 Mikroorg. 



