A program of entomological surveillance was conducted for two years (1974-1976) along the Transamazon Highway, Par?, Brazil. Routine collections from human bait were performed to characterize the available habitats by their respective groupings of hematophagous insects most likely to transmit diseases to the colonist populations. A total of 76,804 hematophagous insects were collected from routine surveillance at 12 sites along the highway. Black flies were the dominant daybiting insects in the cleared peridomiciliary habitat. The cleared areas around houses were effective daytime barriers to all the other hematophagous insects. Biting midges were active in the forest during daylight; but peak activity occurred at night, at which time some midges were caught in the peridomiciliary enviromnent as well. Sand flies were rarely collected outside the forest and were mainly night-active. Although mosquitoes were infrequently collected in open areas during daylight, peak nurmbers were collected near houses at night. In comparison, very low numbers were collected indoors (average of 1/man-hr). Only 8 from a total of 64 mosquito species were routinely collected in abundance at all 12 sites. Three of the eight species were codominants in daytime collections on the forest floor, viz., Psorophora albipes (Theobald), Trichoprosopon digitatum (Rondoni) and Wyeomyia aporonoma (Dyar and Knab). Sabethes chloropterus (von Humboldt) and Sa. glaucodaemon (Dyar and Shannon) were dominants in the tree canopy. Anopheles nu?eztovari (Gabaldon) were collected in high frequency and numbers at night in scrub growth near houses. Two other anophelines, An. oswaZdoi(Peryassu) anddn. Ttiannulatus (Neiva and Pinto), also were abundant both day and night in the forest; but only at night in the secondary scrub habitats. The medical importance and pest value of the dominant species, along with that of the other hematophagous insects, is discussed. Based on the vector roles of the insect groups included in this report, and their temporal and spatial distributions, as documented, we believe hunters alongwith forest and field workers were the target populations for the endemic insectborne diseases. This was primarily a result of 1) a general absence at most sites of any endophagic species and 2) the ecological barrier presented by cleared land around the colonists? houses.
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