330 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



was carried out in Yepocapa in the same region as was the first flight- 

 range Study. The precipitation, relative humidity, temperature, and 

 winds were recorded. The methods were similar to that for the flight- 

 range study with the following modifications : Six aniUne dyes were 

 used as markers, each during a 2-day period, resulting in a total of 

 only 12 days on which flies were stained. This procedure made pos- 

 sible the tracing of recaptured flies with an error no greater than one 

 day. Collecting stations were established closer to the release point at 

 the beginning of the study and more distant from it toward the end. 

 Collections were not begun until 3 days after the last release date. 



In all, 40,083 female flies were stained and released. In the 365 

 visits made to the 31 collecting stations on 72 days of the study, 23,315 

 flies were collected, of which 91 were stained. Fifty-four of these were 

 metallicum, 29 ochraceum, and 8 callidum. One of these, a metallicum, 

 was a fly stained and released in Acatenango (second flight-range 

 study, being carried on concurrently). The longevity of the flies, 

 calculated from the time of the release to recapture, was from 3 to 85 

 days. Table 20 presents the longevity of the recaptured stained flies. 

 The data also include three flies that had been released in this study 

 and were recaptured in Acatenango. Obviously, the findings repre- 

 sent only an approximation of the natural longevity of the flies, since 

 it is unknown how long these wild flies had been living prior to stain- 

 ing, or how much longer they would have survived had they not been 

 killed for examination after recapture. 



Flight range and longevity of infected flies. — To determine whether 

 or not infection with larvae of Onchocerca volvulus affects the flight 

 range and longevity of the black flies, similar studies to those reported 

 in the two preceding sections, but using infected female flies, were 

 carried out by Dalmat and Gibson (1952). The area used was the 

 Municipality of San Pedro Yepocapa, site of two of the previous in- 

 vestigations. The field experiments lasted 83 days, during which 

 period records were kept of precipitation, relative humidity, tempera- 

 ture, and winds. Flies were marked with six dyes, each on 2 consecu- 

 tive days, resulting in a total of only 12 days on which flies were 

 stained. This procedure made possible the tracing of recaptured flies 

 with an error no greater than one day. 



The human subjects used as bait for collecting flies that were to be 

 stained and released had all been previously shown to have heavy 

 infections of microfilariae of Onchocerca volvulus and had all demon- 

 strated their ability to infect wild flies. In order to secure adequate 

 human subjects for infecting the flies, two criteria were adopted: 

 (i) The individual had to show active microfilariae in at least two of 



