Alate wing-dropping is a distinct behavior during the events from flight to colony foundation in termites. In the present study, we examined the alate density effect on the wing-drop in the Formosan subterranean termite Coptotermes formosanus. Alates were collected from field light traps and from field collected colonies kept in the laboratory. Alates were placed in Petri dishes at different densities of 1, 3, 5, 7, 10 and 20 alates/dish. One hour after treatment, both the mean number of dropped-wings and the mean percentage of dealates decreased significantly with alate density increase. Workers significantly inhibited alate wing-drop, whereas soldiers and dead alates had no effect on wing-drop.