314 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



ADULT FLIES 



ANTHROPOPHILIC SPECIES 



The following discussion is concerned almost entirely with the three 

 principal anthropophilic species, Simuliiim ochracewm, metallicum, 

 and callidum. Summarized in table 34 of Appendix III are the feeding 

 and resting habits of three other less important species attacking man, 

 S. veracrusanum, haematopotum, and exiguum. 



Host Preferences 



To determine which species of Guatemalan black flies preferred 

 human hosts and which preferred other animals, two series of experi- 

 ments were organized. In the first experiment, several groups of men, 

 composed of two individuals each, were set out in areas where black 

 flies were abundant. One individual of each group served as a subject, 

 removing all clothing from the feet and from the waist up, and rolling 

 up his trouser legs ; the other person collected specimens as they began 

 to bite the subject. This type of collection was made at every oppor- 

 tunity — at the same time larval and pupal collections were being made 

 throughout the country, or when groups were specifically designated 

 for that purpose. 



Of the 41 species now known to exist in Guatemala (see section 

 entitled "Entomological Studies in Guatemala"), the following 8 have 

 been found to bite man in nature : 



S. metallicum S. veracrusanum 



S. ochraceum S. haematopotum 



S. callidum S. downsi 



S. exiguum Cnephia pacheco-lunai 



Of this group, S. downsi and Cnephia pacheco-lunai bite man only 

 rarely, but 6^. exiguum, S. veracrusanum, and ^. haematopotum, which 

 are widespread throughout large regions of the onchocerciasis zones, 

 are voracious biters of man wherever they exist. It will be seen in 

 table 9 that S. metallicum, S. ochraceum, and S. callidum are the spe- 

 cies that attack man most commonly. Although from the table it 

 might be assumed that S. metallicum is more anthropophilic in its 

 feeding habits than vS". ochraceum, the reverse is actually true. Since 

 metallicum is the dominant human biter throughout most of the year, 

 a larger percent of the total number of biting flies collected were of 

 that species. However, considering the preference of ochraceum and 

 metallicum for human or other animal hosts, the former species will 

 be found to be predominantly anthropophilic while the latter tends to 



