Journal of Chemical Ecology, Vol. 30, No. 6, June 2004 (  C 2004) Originally published online May 8, 2004, Rapid Communications, pp. RC157–163 (http://www.kluweronline.com/issn/0098-0331) SEX PHEROMONE OF QUEENS OF THE SLAVE-MAKING ANT, Polyergus breviceps LES GREENBERG, 1∗ ALI ALIABADI, 1 J. STEPHEN MCELFRESH, 1 HOWARD TOPOFF, 2 AND JOCELYN G. MILLAR 1 1 Department of Entomology, University of California, Riverside, CA 92521 2 P.O. Box 16366, Portal, AZ 85632 (Received April 7, 2004; accepted May 6, 2004) Abstract—The sex attractant pheromone produced in mandibular glands of queens of the slave-making ant Polyergus breviceps has been identified as a blend of methyl 6-methylsalicylate and 3-ethyl-4-methylpentanol. In field trials, each compound alone was completely unattractive to males, whereas blends of the two compounds attracted hundreds of males within a couple of hours. Key Words—Polyergus breviceps, queen sex pheromone, methyl 6-methylsalicylate, 3-ethyl-4-methylpentanol, ant, Formicidae. INTRODUCTION The organization of colonies of social insects such as ants (Formicidae) that are made up of thousands of individuals has fascinated mankind for millennia. Within the Formicidae, a small subset of species, the slave-making ants, are obligate so- cial parasites that depend entirely on workers of slave species to carry out the tasks that enable a colony to survive (Topoff, 1999). Here we report the iden- tification of the sex pheromone blend produced by virgin queens of Polyergus breviceps, a slave-making species that inhabits the western United States, where it exclusively parasitizes ants in the genus Formica (Topoff, 1999). Slave raids are conducted in early summer around the onset of summer rains, with raiding columns and winged males emerging from nests in mid- to late afternoon. Vir- gin queens accompany workers in the raiding columns, and during these raids, a queen releases a pheromone that immediately attracts swarms of flying males, one of which quickly mates with her. The newly mated Polyergus queen invades ∗ To whom correspondence should be addressed. E-mail: les.Greenberg@ucr.edu 1297 0098-0331/04/0600-1297/0 C  2004 Plenum Publishing Corporation