Cyclohexylamine inexplicably induces antennae loss in Formosan subterranean termites (Coptotermes formosanus Shiraki): cyclohexylamine hydrogen phosphate salts are novel termiticides.

Background: In experiments with Formosan subterranean termites (Coptotermes formosanus Shirakii), myo-inositol-2-monophosphate as the dicyclohexylammonium salt was tested among other sugar derivatives, and was found to be toxic to C. formosanus when added to a moistened filter paper food source in plastic Petri dishes.

Results: Curiously, over a nine-day period, the moniliform (beaded) antenna of C. formosanus deteriorated in a stepwise fashion with the most distal pseudosegment (bead) turning brown and falling off, followed by the penultimate pseudosegment, sequentially, until 7-9 days when only a stub of the antenna remained. Termites became increasingly moribund with the loss of antennae, and quit normal behavior including consuming cellulose food, and died. sn-Glycerol-3-phosphate as the dicyclohexylammonium salt also gave the same results. Dicyclohexylammonium hydrogen phosphate and monocyclohexylammonium dihydrogen phosphate were synthesized, to find a low-cost form for application to baits, both of which also showed similar toxicity. In a trial with Fibonacci series dilutions of neat cyclohexylamine, the antenna-affecting activity became apparent in the LD (14 days) to LD range of concentrations. At the higher concentrations, darkening of the most distal parts of leg extremities was noticed.

Conclusion: Cyclohexylamine appears to be a novel termiticide with a previously unreported mechanism of toxicity. Its hydrogen phosphate salts retain the toxic effect and are inexpensive and easily synthesized. © 2017 Society of Chemical Industry.