Phenylalkenals in ponerine(Leptogenys sp.) and myrmicine (Pogonomyrmex sp.) ants

Cephalic extracts of two unrelated species of ants,Leptogenys processionalis andPogonomyrmex rugosus, have been found to contain 2-phenylpropenal and 2-phenyl-2-butenal, while two other species related to the first,L. chinensis andL. kitteli, lacked either.L. kitteli also produced a tetrasubstituted pyrazine found previously only in two New Zealand ants in the genusMesoponera. The chemical reactivity of the phenylalkenals suggests their function in repelling attack by predators.