Update on the defensive chemicals of the little black ant, Monomorium minimum (Hymenoptera: Formicidae)

Alkaloids, including 2,5-dialkylpyrrolidines and 2,5-dialkylpyrrolines, have been reported to be components in the venom of little black ants, Monomorium minimum (Buckley). Two fatty amines were recently reported as minor compounds. By analyzing the discharge collected from the stinger apparatus (milking), this study revealed the presence of an additional seven compounds in the defensive secretion of this ant species. Compounds identified were 9-decenyl-1-amine, N-methylenedecan-1-amine, N-methylenedodecan-1-amine, 2-(1-non-8-enyl)-5-(1-hex-5-enyl)-1-pyrroline, N-methyl-2-(hex-5-enyl)-5-nonanyl-1-pyrrolidine, β-springene ((E,E)-7,11,15-trimethyl-3-methylene-1,6,10,14-hexadecatetraene) and neocembrene ((E,E,E)-1-isopropenyl-4,8,12-trimethylcyclotetradeca-3,7,11-triene). β-springene and neocembrene were found only in the defensive secretion of queens. Analyses of the contents of isolated poison and Dufour's glands of the queen indicated that all amines and alkaloids were from the poison gland and that β-springene and neocembrene were from the Dufour's gland. This demonstrated that the defensive secretion in M. minimum queens consists of components from both glands. This is also the first report on the natural occurrence of 9-decenyl-1-amine, N-methylenedecan-1-amine, and N-methyllenedodecan-1-amine.