334 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



onchocerciasis in Guatemala, it would seem advisable to attack both 

 the infected and uninfected flies. 



Resting Places and Height Range of the Adults 



It is common knowledge that different groups of insects, as well as 

 different species within a single group, may have different resting 

 habits and habitats. Thus, before considering a control program di- 

 rected against adult black flies, it was of prime importance to learn 

 on what surfaces they alight. Much money and effort may be spent 

 uselessly by treating with insecticides areas where the black flies will 

 not be affected. 



Since no data concerning the resting places of adult Simuliidae had 

 been published up to the time of these studies, it was deemed advisable 

 to initiate appropriate investigations. The first hint as to where the 

 flies rest at night was obtained indirectly and quite by chance. In an 

 attempt to establish a self -perpetuating colony of black flies (see 

 "Colonization of Black Flies" in this section), a very large metal- 

 screen cage was constructed and placed over a water channel that was 

 diverted so that it passed through the laboratory property. Some of 

 the same plants found at the breeding places of the flies and in the 

 fields of the coffee plantations were planted within the cage. Thou- 

 sands of flies were introduced into the cage where they were pre- 

 sented with human subjects for blood meals, in the hope that they 

 would oviposit in the running water below. 



In the course of observations, it was found that caged flies that were 

 active during the day were not visible at night. A careful search did 

 not reveal them. In the morning following, a large number of flies 

 were again seen in the cage. Continuous observations throughout the 

 day disclosed that as the sun set, the flies migrated to lower levels in 

 the cage until at nightfall the flies actually worked their way down to 

 the bases of plant stems close to the ground level or, at times, slightly 

 beneath the surface. Repetition of these observations stimulated fur- 

 ther field studies. 



Teams of men, equipped with Coleman lanterns, white cloth, and 

 collecting tubes, were placed in areas of the plantations known to 

 harbor heavy black-fly populations. It was found that after a lo- to 

 15-minute initial wait, small numbers of flies were attracted to the 

 brilliant light and could be collected from the white cloth which had 

 been placed beside the lamp. Females as well as a few males were 

 taken in this fashion. After numerous observations of this sort, it 

 was finally possible to establish that the flies were emerging from their 

 night resting places close to the surface of the ground. 



