Isolation, identification, synthesis and biological activity of volatile compounds from the heads of Atta ants.

S-(+)-4-methyl-3-heptanone has been identified as the principal alarm pheromone of Atta texana and Atta cephalotes. Both enantiomers of 4methyl-3-heptanone have been synthesized and their biological activities have been compared on both species of ants. Comparison of the geometric averages of response ratios, at threshold concentration levels on A. texana, showed S(4)-4-methyl-3-heptanone to be about 100 times more active than the (-) enantiomer. A similar analysis also showed no inhibition of the activity of S( + )-4-methyl-3-heptanone by the () enantiomer. A less rigorous study on A. ceplzalotes showed S-(+)-4-methyl-3-heptanone to be about 210 times more active than R-( )-4-methyl-3 -heptanone. Both ant species produce 3-octanone, possible trace amounts of 3-octanol, and both diastereomers of 4-methyl-3-heptanol. A. texana also produces (+)-2-heptanol, 2-heptanone, and 3-heptanol. A. cephalotes contains trace amounts of 2-heptanone.