Semi-Centennial Volume. 65 



Occurrences of Black Flies in Louisiana During Recent Years. 



Elbert S. Tucker, 

 Louisiana Asricultiiral Experiment Stnfioii, liaton Koiifie. 



Severe outbreaks of black flies in Louisiana seem to be known more 

 as events of the long- past than of recent memory. Nevertheless, the 

 insects have doubtlessly occurred every season throughout the later 

 period, either to a negligible extent or occasionally in greater force under 

 especially favorable conditions, as will be noted, in various localities in 

 the northern half of the state. Still no complaint of the pests has been 

 reported directly to the state entomologist for several years back, or at 

 least not since the beginning of 1912. In the files of his office, however, 

 are two reports of investigations made by former agents in regard to 

 local plagues caused by such foes. 



Owing to the special interest which was rather recently accorded to the 

 different species of Simidium on account of the suspicion that came to be 

 advanced implicating them as conveyors of pellagra, the writer under- 

 took to secure the later facts concerning their existence in Louisiana. 

 As a result, all of the available information which was thus obtained 

 but not heretofore appearing in print is now pi-esented in the following 

 accounts: 



Personal encounters with black flies on his home farm at Logansport, 

 De Soto parish, has made Mr. J. B. Garrett well acquainted with the 

 pests. He has stated that in 1897 the flies appeared in such numbers as 

 to harass mules while being used for plowing fields at the time. The in- 

 sects were then especially troublesome in places along the edges of over- 

 flowed land. In order to work the mules in the bordering fields during 

 the height of the prevalence of the flies, the animals were smeared with 

 grease to protect them from bites. While the pests spread into the 

 country a few miles away from their breeding quarters within the flooded 

 areas, they were not known to attack persons. Even though they 

 gathered in such masses on the mules as to mat themselves among the 

 hairs, particulaily clinging to the flanks, yet the men working the 

 animals in the fields were only annoyed by the insects flying about the 

 face. On his part, Mr. Garrett has never been bitten by any kind of 

 the flies, notwithstanding the fact that he has been repeatedly exposed 

 to swarms of them. To the best of his recollection, three successive 

 yearly outbreaks occurred, beginning late in February and lasting up 

 til about the middle of March. Each time was marked by high water in 

 the Sabine river, which overflowed swamps and lowlands adjacent to 

 its banks. After the water receded, great numbers of pupal cases hung 

 on bushes that had been swept by currents of the flood. 



In years when the river did not overflow to much extent or not at all, 

 scarcely any black flies appeared, although larvae could sometimes be 

 found on bushes, logs and dead branches submerged at the edge of the 

 banks. The conditions for the breeding of the flies in troublesome num- 

 bers were always due to extensive spring overflows. 



On March 2.3-24, 1908, after a period of rainy weather, the writer 

 visited Logansport, but found no black flies, since the river had remained 

 at a low stage. 



5 — Acad. Sci. — 2199 



