NO. I BLACK FLIES OF GUATEMALA — DALMAT 3I3 



rock, lands only long enough to deposit one egg, then flies away to 

 repeat the process on another suitable surface. On occasion, females 

 may deposit several eggs on one surface in an irregular group which 

 is covered by a dark viscous material to which sand and minute parti- 

 cles of debris become attached. At times, three to five females have 

 been observed in the process of ovipositing in the same area. The 

 individual eggs or egg groups can be found only after long and careful 

 observation, since they are well camouflaged by the dark viscous ma- 

 trix. The young larvae emerge after 3 to 8 days and then migrate, 

 approximately 50 percent of the larvae attaching to leaves, the other 

 50 percent choosing stones, twigs, and debris in about equal numbers. 

 The larval stage lasts from 8 to 25 days and the pupal stage lasts from 

 3 to 6 days, after which the adult emerges. The females of this species 

 can survive at least 20 days in nature (see "Flight Range and Longev- 

 ity" in the section on ecology, and Appendix III, table 32). 



OTHER SPECIES 



Since the principal anthropophilic species are those of major im- 

 portance when considering the transmission of onchocerciasis, studies 

 were made of the developmental cycle of only very few other species. 

 The results are charted below in table 11. 



Table ii. — Life history of some Guatemalan Simuliidae 



Species Feeding preferences 



S. (L.) veracrusanum Human and other 



animal hosts 

 S. (L.) downsi Zoophilic, rarely 



biting man 



S. (D.) mexicanum Zoophilic 



S. (D.) rubicundulum Zoophilic 



Gigantodax aquamarensis . . Zoophilic 



ECOLOGY 



In the following discussion, everything related to the habits of the 

 black flies and their relationship to the environment has been included. 

 General discussions of geography and climate, plant associations, ani- 

 mal associations, and stream types found inside and outside of the 

 onchocerciasis zones have already been given in the section on epi- 

 demiology, since these factors influence the presence or absence of the 

 disease in particular regions, as well as its spread to new areas. They 

 will again be incorporated in the following discussions, but only insofar 

 as they bear directly on the subject being treated. 



