Objective: To establish an efficacious and efficient surveillance method of Armigeres (Ar.) subalbatus, a known filarial vector, surviving in forest habitats to estimate realistic population density and assess the impact of altitudinal variations on the efficacy of the trap. Methods: In the study, 12 locations in areas with an altitudinal range from 82 m to 920 m were selected in three reserve forests for night sampling of adult Ar. subalbatus mosquito using standard chemical lure based BG-Sentinel traps and CDC-light traps in pairs. Effects of locations and time were estimated on the efficacy of traps as mosquito density using multifactor analysis of variance for significant differences. Impact of altitudinal variations on the efficacy of traps was assessed using multiple regression with slope comparison. Results: BG-Sentinel trap collected significantly more adult Ar. subalbatus, 4.43 folds in Gorumara NP, 5.19 folds in Neora Valley NP and 12.10 folds in Mahananda WLS than the CDC-light trap irrespective to locations. BG-Sentinel traps were tolerant of altitudinal variations (80 m -170 m) and showed no significant relationship between density and altitudes in contrast to CDC-light traps which showed a significant negative impact on capturing efficacy with increase in altitudes (P<0.001). Conclusions: The study suggests that BG-Sentinel traps can be used effectively and efficiently to collect more Ar. subalbatus mosquitoes during night time in comparison to CDC-light trap under complex climatic conditions of forest and variable altitudes.