February, '10] SANDERSON : BLACK FLY 27 



CONTROLLING THE BLACK FLY IN THE WHITE 



MOUNTAINS 

 By E. DwiGHT Sanderson. Durham, JV- H- 



In 1904^ Dr. C. M. Weed showed that the larvae of the black fly 

 might be destroyed by an application of phinotas oil and -later Mr. 

 A. F. Conradi, who performed the experiments, gave a further report. - 

 The experiments at Dixville Notch conducted at that time were en- 

 tirely successful, and but very little trouble has been experienced from 

 black flies in that locality since then. 



For the past few seasons the residents at Appalachia in the valley 

 immediately north of the Presidential Kange, have been greatly an- 

 noyed by the black flies and appealed to us for some practical means 

 of controlling the pest. It was found that the neighboring streams 

 were alive with the larvae, and in view of the previous experiments it 

 seemed entirely feasible to destroy them by the use of phinotas oil. 

 My assistant, Mr. W. M. Barrows, spent the greater part of the month 

 of July at Appalachia investigating the habits of the flies and in mak- 

 ing experiments for their control. Two species occur commonly, the 

 white legged variety {Simulium venustum) causing very little annoy- 

 ance, the biting being done by Simulium hirtipes. The life history of 

 these species is unknown in this region. There is a general belief 

 among the inhabitants that the flies are to be found over winter in 

 the timber, and reliable observations are given us of parties being- 

 troubled by the biting of the black flies high up on the mountains the 

 second of October after there had been a heavy snow and frost in 

 the valley. It has been supposed by -some observers that the small 

 larvffi passed the winter on the stones ; in any event the flies are more 

 numerous during early summer and again in later summer. In early 

 July we found but few young larvae and were unable to find the eggs, 

 most of the larvaa being full grown and pupating. By the middle of 

 July many flies were emerging from the pupte. It is evident that if 

 the flies hibernate they would be unable to deposit their eggs until 

 after the high water of spring subsided. An accurate knowledge of 

 the life history of the insect will be absolutely necessary in order to 

 determine the best season for carrying on measures of control by oil- 

 ing and will probably also have an important relation to the effect of 

 the oil on the fish. 



It was found that phinotas oil applied to the stream by throwing it 



' Bulletin 112, N. H. Agr. Experiment Station. 



= See Bulletin 52, Div. of Entomology, U. S. Department of Agric-ulture. 



