THE MANDIBULAR GLAND SECRETIONS OF THE LEAF-CUTTING ANTS Atta sexdens sexdens AND Atta opaciceps EXHIBIT INTERCASTE AND INTERCOLONY VARIATIONS M. R. FRANCELINO, A. L. MENDONC ¸ A, R. R. DO NASCIMENTO,* and A. E. G. SANT’ANA Laborato ´rio de Ecologia Quı ´mica, CCEN, Universidade Federal de Alagoas, Campus A.C. Simo ˜es, Br 104 Km 14, 57072-970, Maceio ´-AL, Brazil (Received February 23, 2005; revised November 8, 2005; accepted November 9, 2005) Published Online April 25, 2006 Abstract—The mandibular gland secretions of worker castes from wild colonies of the leaf-cutting ants Atta sexdens sexdens and Atta opaciceps were analyzed quantitatively by gas chromatography–mass spectrometry. The secretions comprised a complex mixture of volatile, mainly oxygenated compounds, and their profiles exhibited considerable qualitative and quanti- tative variations among species and castes. The known alarm pheromone 4- methyl-3-heptanone was common to both species. The elevated relative proportions of this ketone found in the secretions of gardeners and generalists suggest that such castes are primarily responsible for the production and release of the alarm pheromone. Quantitative variations (but no qualitative differences) in the profiles of secretions of soldiers from different colonies of A. sexdens sexdens were detected, supporting the view that intraspecific colony recognition is mediated through mandibular gland secretions. Subsequent laboratory assays showed that, among the compounds identified by GC–MS, 4-methyl-3-heptanone elicited a strong alarm response in workers of A. sexdens sexdens and A. opaciceps. Key Words —Alarm pheromone, Atta sexdens sexdens, Atta opaciceps, hymenoptera, formicidae, myrmicinae, attini. 0098-0331/06/0300-0643/0 # 2006 Springer Science + Business Media, Inc. 643 Journal of Chemical Ecology, Vol. 32, No. 3, March 2006 (#2006) DOI: 10.1007/s10886-005-9020-9 * To whom correspondence should be addressed. E-mail: rrn@ccen.ufal.br