166 INSECTS 



formed so as to be able to ouncture the skin of the host 

 and to suck the blood beneath it. In almost every 

 instance the early stages are passed elsewhere than on 

 the host that serves as food in the adult stage, and some- 

 times not even in the same medium. The mosquitoes, 

 for instance, attack all sorts of vertebrates, cold-blooded 

 as well as warm-blooded; but so far as known, all the 

 larvse are strictly aquatic, dwellers in water and adapted 

 to secure their food only in that medium. Yet while 

 the direct relations between animals and mosquitoes 

 are simple enough, the indirect influence that they 

 exert as intermediate hosts for certain disease-produc- 

 ing organisms are of so great importance as to require 

 more specific treatment in another connection. 



The SimuliidcB, containing those species known as 

 "black flies," "midges," "Buffalo gnats" and others 

 of similar character, are in somewhat the same case. 

 The adults feed on warm-blooded animals, the larvae 

 are found only in water usually adhering to stones, 

 logs, roots or other points of attachment and gaining 

 their food supply entirely from beneath the surface. 

 As both mosquitoes and gnats develop in water, their 

 presence as adults in some localities is coincident, and 

 a better combination for making life miserable can 

 scarcely be imagined. The gnats are preferably day 

 fliers, the mosquitoes preferably night fliers, so the 

 entire diurnal cycle is thus provided for. The "black 

 flies" do not worry their victims by buzzing or "sing- 

 ing." They are extremely business-like in their method 

 and as soon as they alight they set to work. Their 

 puncture is recognizable at once and resembles the 

 prick of a hot, very fine needle, much more than any 

 other bite known to me. The mouth parts are short, 

 not nearly so compact as those of the mosquitoes, and 

 the flies appear to veritably dig into the skin leaving, 



