494 REPORT OP THE COMMISSIONER OF AGRICULTURE. 



In 1861 and 1862 they were very troublesome in portions of Missis- 

 sip|)i and Louisiana; in 1863 and 1864 they abounded about Shreveport, 

 La., and in Chicot County, Arkansas. None are reported to occur 

 m 1865. but in 1866 they invaded the alluvial country between the 

 Arkansas and Red Rivers east of the Washita. In 1873 and 1874 

 serious injury was occasioned by them in several regions in Louisiana. 

 But in ISS'i and 1884 they were more destructive than ever before, 

 doing immense damage to live stock of all kinds. Although not gen- 

 erally very numerous in 1885, they appeared in sufficient numbers in 

 several counties of Louisiana to kill quite a number of mules. In 

 1886 they appeared generally throughout the whole extent of the 

 region infested by them, and'they appeared rather unexpectedly, be- 

 cause it was so unprecedentedly late in the season. 



In Indiana this insect was well known as far back as 1843, when 

 the settlers used to watch for it every year, as swarms would appear 

 in certain regions with more or less regularity, often occasioning con- 

 siderable damage. 



It was ascertained from a number of gentlemen in Tennessee and 

 Mississippi that the Buffalo Gnats were well known to their ancestors 

 who first settled in that region at a time when Indians were their 

 neighbors. 



But every one questioned in the States of Louisiana, Mississippi, 

 Tennessee, and Arkansas would voice this universal opinion, viz, that 

 Buffalo Gnats come only with high water and are contemporary with 

 an overflow. The connection between an overflow and the appear- 

 ance of the Buffalo Gnats will be considered farther on. 



TIME OF APPEARANCE. 



The time of the appearance of the Southern Buffalo Gnat is regu- 

 lated by the earliness or lateness of spring, and it consequently ap- 

 pears much earlier in the southern parts of the Mississippi Valley. 

 As a rule, it can be expected soon after the first continuous warm si)ell 

 in early spring. The first svv^arms were observed last year in Louisi- 

 ana on March 11; in Mississippi and Tennessee, May 1; and in Indi- 

 ana and Illinois, May 12. Small and local swarms may appear some- 

 what earlier or later in the neighborhood of their breeding-places. 

 The Turkey Gnat appears usually later, although in 1886 it appeared 

 near Memphis, Tenn., as early as April 5; the swarms were quite 

 local, however, and strictly confined to the vicinity of creeks tJiat 

 produced them. In Louisiana they appeared, as usual, much later 

 than the true Buffalo Gnat, and some were found as late as June 6, 

 and the bayous disclosed others still in their pupal state. 



The great majority of the species of this genus are northern insects, 

 and appear there in the winged form all through the summer. The 

 larva? require cold water for development. As we go farther south 

 this cold water can only be found in the more elevated regions or in 

 winter or the early months of spring. Earliness of season or high 

 altitude are there the substitutes for the lower temperature of more 

 northern latitude. 



DURATION OF AN INVASION. 



Swarms of Buffalo Gnats usually appear with the first continuous 

 warm weather of early spring. They lead a roA'ing kind of life, be- 

 ing drifted about with the wind, which frequently carries them long 



