Fipronil is very active against termites, topical application providing an LD50=0.16 ng/termite. When exposed to 1 ppm of C¹⁴-fipronil for 1 hr and 4 hr, individual termites were able to pick up 0.33 ng and 1.56 ng of active ingredient, respectively. Percentage mortality was 100% after 3 days in termites exposed to 1 ppm for 1 hr. When donor termites exposed to 1 ppm for 1 hr were mixed with naive termites (recipient) for 24 hrs, it resulted in 94% and 68% mortality in donor and recipient termites at day 7, respectively. To study the horizontal transfer of fipronil as a cascade event, the1st batch of recipient termites acted as 2nd donors for 2nd batch of recipient termites. When 2nd donors were mixed with naive recipients (2nd recipients), there was 86% mortality of the 2nd donors and only 2% mortality in the 2nd recipients. Thus, fipronil is effectively transferred from the original donors (exposed to 1 ppm for 1 hr) to 1st batch of recipients but not further down.