NO. I BLACK FLIES OF GUATEMALA — DALMAT 33 1 



four cutaneous biopsies ; and (2) flies which were fed on the individual 

 had to ingest microfilariae of Onchocerca volvulus and support normal 

 development of the parasite for at least 72 hours under laboratory- 

 conditions. In all, 213 individuals were examined by the skin-biopsy 

 technique, of whom only 16 satisfied the first criterion of two positive 



Table 20. — Longevity of anthropophilic simuliids 



Number of stained flies recaptured 



Longevity Simulium (S.) Simulium (S.) Simulium (L.) 



(days) metallicum ochraceum callidum 



3 2 — 2 



5 I 13 — 



7 9 5 I 



9 I — — 



10 3 I I 



II 7 — — 



12 — I — 



13 I I — 



14 — 2 — 



17 I — — 



20 — — I 



21 I 2 — 



24 I — — 



25 16 4 — 



26 2 — — 



27 I I — 



38 I - - 



39 I — — 



41 3 — — 



52 I — — 



64 I — — 



66 I — — 



68 I — — 



72 2 — — 



75 I — — 



77 I — — 



8S I - - 



Totals 60 29 5 



biopsies among the four which were taken. These 16 individuals were 

 then tested for their ability to infect flies by allowing approximately 

 100 simuliids to feed on each person. The flies were then maintained 

 in the laboratory. Those flies that died before the third day were 

 discarded ; those that lived 3 days or more were dissected immedi- 

 ately after they died to determine if they had become infected. On 

 the basis of these dissections, the six individuals who produced the 



