REPORT OF THE BUREAU OF ANIMAL INDUSTRY. 465 



PROBABILITY OF FUTURE INVASIONS. 



If, in the future, the conditions favorable to the development of 

 these gnats in such immense numbers remain as in the past, it is 

 but proper to assume that the effect will be much the same. But as 

 we have stated, it is not probable that the present state of the levees 

 will continue even another year. Just what effect the confinement 

 of the Mississippi River to its proper channel below the mouth of the 

 Arkansas, in extreme high water, will have upon the St. Francis 

 River, and the country between it and the Mississippi itself, is a 

 problem which even civil engineers themselves can not yet decide. 



If the St. Francis bottoms remain as they are now, unprotected by 

 levees, and the current of that stream is not materially affected or 

 changed from its present condition, there is little hope in the future 

 for immunity from gnats throughout eastern Arkansas, west Ten- 

 nessee, and northwest Mississippi in the event of high waters during 

 March and April. 



Overflow from the Mississippi River gains admission into the St. 

 Francis through the region known as "sunken lands," in the vicinity 

 of New Madrid, Mo. With water at 39.6 on the gauge at Cairo, 111., 

 the overflow first begins, and a height of 44.0 or above at the same 

 place, for any considerable length of time, is sufficient to inundate 

 the greater portion of the St. Francis bottoms. Hence, unless nega- 

 tive factors, not now known to exist, should arise and the water 

 should remain for any considerable time, between March 15 and April 

 25, at or above 44.0 on the gauge at Cairo, an invasion of gnats more 

 or less serious may be expected. 



The direction and velocity of the wind, during an invasion of 

 gnats, no doubt exert considerable influence in distributing them 

 over the country, and therefore, with west, southwest, or northwest 

 winds, they would be carried into west Tennessee and northwest 

 Mississippi; while the reverse of these would carry them farther 

 into the interior of Arkansas, and, to some extent at least, protect 

 the former localities. 



SUGGESTIONS. 



* ' i 



From the preceding it will be clearly observed that trouble from 

 gnats, in the future, is to be apprehended, particularly throughout 

 eastern Arkansas and the adjacent country. For a considerable time 

 to come the stock- raisers and the dairymen throughout a section of 

 country of which Memphis, Tenn., may be considered the center, 

 will be obliged to contend with this, the greatest drawback of both 

 industries. 



What these people at present most need is (1) a better knowledge 

 of the effects of the bites of gnats on the animal system, and the 

 best means of counteracting these effects; (2) the relation of the bites 

 to charbon, and relief for this disease ; and (3) some substance which 

 can be applied externally to animals to protect them from the bites 

 of gnats, and is not itself injurious to the animals to which it is 

 applied. For the purpose of this, I would strongly recommend the 

 detail of a competent veterinarian during the next invasion of gnats, 

 whose duty shall be to study these points, and to enlighten people 

 thereon-. 



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