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 LD30 (14 days) to LD70 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