Population dynamics and seasonal occurrence of adult Amphipsyche meridiana Ulmer, 1902 (Trichoptera: Hydropsychidae) in an irrigation pond outlet at Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom Province were determined, with the influence of air temperature, wind speed, precipitation and relative humidity on its population density being evaluated. Samples were collected monthly from January to December 2013 by light trapping. Monthly sampling records for adults collected were 24876, 2605, 29344, 43632, 18684, 16524, 29871, 15183, 10548, 17100, 7695 and 15678, respectively. An increase in the number of adults collected was observed from January to July with peaks of 43,632 (18.83%) in April. A remarkable decrease in the number of insects collected was observed in the months after August. There was an increase in the number of adults most influenced by the decrease in precipitation and relative humidity.