46 



Economic hnportaiice and relation to disease — Direct injuries 

 not only annoying to man and animals but may be serious. Occur 

 in enormous numbers in some regions, rendering them uninhabitable. 

 Deprecation of real estate, retarding development of many localities. 

 As disease carriers, they are the sole agents in transmission of malaria, 

 yellow fever, filariasis and are suspected of directly transferring 

 some other diseases. 



Methods of combatting — Efforts should be directed against the 

 larvae. Destruction of breeding places; drainage; oiling; introduc- 

 tion of minnows and other small fish. Screening against adults, 

 necessity of screening patients with mosquito-born diseases. 



Family SIMULIIDAE, the black flies. Illustrated by : 



Simulium pecuarum, the bvffalo gnat. Causes enormous losses 

 of horses, mules, and other domestic animals in the Mississippi 

 Valley. See Osborn, '96, 



Description — Size minute, about 6 mm. long, body short and 

 stout, color black, but body covered with grayish-brown, short and 

 silken hairs. Antennae 10-jointed, scarcely longer than head; 

 wings without scales. 



Life history — Early stages aquatic. Eggs laid in patches on rocks, 

 submerged stumps, brush, etc., in rapidly moving water. Larvae 

 slender, cylindrical, closely crowded so as to appear like dark patches 

 of agal growth on the objects to which they are attached (see patches 

 on the brinks of falls or in rapids of any of our local streams) . Pupal 

 case conical, grayish or brownish, and has its upper half cut squarely 

 off, more or less raggedly. Time of appearance of adults varies 

 with the earliness or lateness of the spring, and consequently much 

 earlier in the southern parts of the Mississippi Valley. 



Habits of adults and economic importance — Blood-sucking exceed- 

 ingly active, appear in enormous swarms, attacking domestic animals 

 and not infrequently causing death. No evidence that losses are 

 due to a specific disease transmitted by the fly but rather to loss of 

 blood and terrible irritation caused by the myriads of poisonous bites. 

 Area infested, in the worst years, all of Mississippi Valley from the 

 mouth of the Red River, in Louisiana, to St. Louis, Mo., and land 

 adjacent to the tributaries of the Mississippi River in these regions. 



Methods of combatting — Destruction of larvae not feasible. As 

 preventives, smudges in fields and yards or even in pails suspended 



