496 KEPORT OF THE COMMISSIONER OF AGRICULTURE. 



them aAvay from his face, which does not alwaj^s prevent them from 

 entering and filling his mouth, nose, and ears; he is so tormented by 

 them, and frequently by their bite as well, that he has to cease work- 

 ing for the time being. Thousands try to enter the houses in vil- 

 lages and cities, and the windows are frequently completelj- covered 

 with them. 



MODE OF ATTACK. 



The flight of all species of Simulium is very swift and powerful. 

 They possess, in comparison with most other flies, an enormously 

 large thorax, consisting of a very tough, chitinous integument, that 

 furnishes ample attachment for the strong muscles which propel them 

 during their long and continuous flights. 



The Southern Buffalo Gnat is exceedingly active in all its motions, 

 and is at its bloody work as soon as it has gained a foothold upon an 

 animal. The individual flight is inconspicuous and rarely more than 

 a few feet from the ground. It is also usually noiseless, but when one 

 passes rapidly close to the ear of a person the sound produced is faintly 

 like that of a passing bullet, and no one who has listened to it will 

 ever forget it, but will always connect it with their presence. 



If the insects are not very hungry, or if influenced by too warm or 

 too dry an atmosphere, they circle around a mule or a horse very 

 much like so many small bees; if hungry, however, they lose no time 

 whatever, but with a few nervous jerks settle upon the selected spots 

 and immediatel}^ go to work. They are never quiet, but are most 

 active during early morning and towards evening. They also fly dur- 

 ing moonlight nights. During the hottest portions of the day, from 

 11 a. m. to 4 p. m. , they are more or less inactive. Their favorite time 

 of attack is a cloudy, dark day, or when rain is threatening. If the 

 gnats try to enter houses or stables by means of the windows, they 

 constantly butt their heads against the panes of glass, until they be- 

 come so exhausted that they drop to the ground and die. Specimens 

 kept in confinement in large vessels, with the bottoms covered with 

 moss and soil and containing a wet sponge and a saucer filled with 

 water, die within forty hours. During all this time they never cease 

 trying to escape. The sense of smell (and sight) of these insects must 

 be well developed, because they unerringly find animals a long dis- 

 tance away from their breeding-places. If very numerous, they cover 

 the whole animal, without making any selection of position. 



The smaller Turkey Gnats are not so blood-thirsty, nor do they form 

 such large swarms. The snorting, biting, switching of tails, and the 

 general restlessness of the stock in the fields soon reveal the presence 

 of their foes. The gnats will, upon arrival, rapidly circle around the 

 animal, select a point of attack, fasten themselves upon the chosen 

 spot, and immediately commence to bite. The genital and anal re- 

 gions, the ears and portions of body between the forelegs — in short, 

 those parts where the skin is most easily punctured— are selected by 

 these insects. The attack is so rapid, that in course of one minute the 

 body of the tormentor is seen to expand with blood, which shows 

 plainly through the epidermis of the abdomen. The bitten part of 

 the animal shows a nipplelike projection, and if the insect is removed 

 by force a drop of blood as large as a good-sized pin's head will ooze 

 out. Other gnats will almost at once pounce upon the same spot and 

 continue the biting. All those veins which project under the skin of 

 the animal are also favorable points of attack, and their course is made 

 visible by the hordes of gnats fastened upon thein. 



