484 OTHER IJLOOO-SUCKIXG FLIE8 



flies if it does not cliniinato them entirely. In such cases care 

 should i)e taken that there are no small trickling streams which 

 are not readily reached by fish. In the author's experience 

 streams which harbor large numl)ers of caddis worms, dragon-fly 

 larvffi and other carnivorous aquatic insects do not breed black- 

 flies to any extent. 



A considerable degree of protection from blackflies can be 

 obtained In' the use of repellents such as are used for moscjuitoes, 

 but their efficiency seems to be lost more quickly than in the case 

 of mosquitoes. Moreover the crawling habits of the flies must 

 be taken into account, and other parts of the body than tho.se 

 which are directly exposed nmst be treated. Blackflies may be 

 driven from houses by fumigation with py ret brum powder or by 

 any other fumigation method. In camp life the use of smudges 

 is indispensable. An efficient smudge which will last all night 

 can be made in an old bucket with a few holes punched near the 

 bottom. A small fire is started in this and then the bucket is 

 filled with partly wet, punky, decayed wood which will smoulder 

 slowly and produce a dense yellow smoke. Sleeping in the 

 presence of such a smoke is at first almost as unpleasant as are 

 attacks by mosquitoes and blackflies (the latter becoming active 

 only toward dawn) but one soon becomes accustomed to it, 

 and it has none of the terrible after-effects of an attack by the 

 flies. 



Gadflies (Tabanidae) 



General Account. — Although primarily of importance as 

 l)lood-thirsty pests of domestic animals, the gadflies or hor.seflies 

 (Tabanidae) cannot be ignored as biters of human beings, es- 

 pecially as they have been shown to be implicated in tlic spread 

 of certain human diseases. The bites are jiaiiiful, and som(^times 

 cause annoyance for several hours; not infnviuently these bites, 

 which may bleed, subsequently l)ecome infected and give rise 

 to troublesome sores. The females alone are bloodsuckers, th(> 

 males living chiefly on plant juices. These flies, of which over 

 2r)f)0 species have been recorded, occur in every part of the world, 

 and in every sort of habitat where water or damp places are avail- 

 able for breeding purposes. 



The gadflies are of large size and heavy build (Fig. 224 A). 

 They are often beautifully colored in black, brown and orange 



