The evening crepuscular host-seeking activity of Anopheles mosquitoes in northeast Brazil.

Studies on the timing of anopheline host-seeking are important for understanding mosquito ecology, behaviors, and possible role in disease transmission. To study the evening crepuscular host-seeking activity of anophelines and the effects of moonlight, anopheline mosquitoes were collected with light traps settled in a livestock area in the Brazilian Cerrado region. Traps (Silva traps) were placed next to animal enclosures at 1.5 m asl. The research was divided in 2 experiments: the first experiment (12 nights) comprised 2 trapping periods, one from 6 PM to 7 PM and one from 7 PM to 6 AM, and the second experiment (16 evenings) divided in three 20-min intervals based on the 3 twilight phases (civil: 6-6:20 PM; nautical: 6:20-6:40 PM; and astronomical: 6:40-7 PM). A total of 2,815 anopheline mosquitoes and 9 species were found. The main species were Anopheles triannulatus s.l., An. argyritarsis, An. goeldii, and An. evanse. Host-seeking mosquitoes were more frequently active during the first hour after sunset, with a significant peak in the second 20-min interval. After that, a decrease in the number of individuals was observed from the astronomical twilight onwards. Moonlight did not affect the evening flight activity of anophelines. By using LED-based passive light traps, the evening arrival time of anophelines at blood-feeding sites was demonstrated, and it may be a key time window for malaria vector control interventions.