342 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I25 



are also misleading since they appear to indicate that dogs are the 

 principal hosts of this species and humans the secondary ones. The 

 fact is that, other than man, only dogs were used as bait in the region 

 where haematopotum is abundant. Probably several other animals 

 could have been shown to be equally suitable hosts had they been 

 exposed to the bites of the flies. 



It would seem from table 9 that S. exiguum and veracrusanum 

 seldom bite man. This erroneous impression is given since the table 

 does not actually compare the preference of a particular species of 

 black fly for various hosts, but rather gives the relative frequency with 

 which the various species of black flies attack a particular host. Ac- 

 tually, exiguum and veracrusanum will attack man voraciously in areas 

 where these species are abundant (see "Reservoirs and Vectors" in the 

 sections on epidemiology and distribution of Guatemalan Simuliidae). 



Simulium ochraceiim and metallicum not only are the principal 

 anthropophilic species, but they are also the species that most com- 

 monly attack animals other than man. When these species are pre- 

 sented with both human and other animal bait, side by side (table 10, 

 p. 46), ochraceum proves to be definitely anthropophilic while metal- 

 licum is seen to be more zoophilic in nature. In table 9, of the total 

 number of flies collected from man, 30 percent were ochraceum while 

 65 percent were metallicum. This can be accounted for when it is 

 realized that, although metallicum is definitely zoophilic, it will attack 

 man freely and it is by far the dominant species (in numbers) of those 

 that bite humans in the onchocerciasis zone where the majority of 

 these investigations were made. 



Numerous experiments were conducted to determine the preferences 

 of various Simulium species for different body parts of the animals 

 they attacked. These data have been presented in Appendix III, 

 table 35. 



IMMATURE STAGES 



Since the members of the family Simuliidae all feed on animals, to 

 collect sufficient adult material of all species for taxonomic studies or 

 to discover their distribution throughout Guatemala for ecological and 

 life-history studies, would require an intimate knowledge of their host 

 preferences. Since the majority of species are not anthropophilic, and 

 since their host preferences are not completely known, it was found 

 most convenient to collect the immature stages and rear them to adults. 

 This was done, using the techniques already described in the first part 

 of the section on taxonomy of the Guatemalan Simuliidae. Along with 

 each collection made, certain information concerning the breeding 



