Journal of Insect Behavior, VoL 9, No. 5, 1996 Postpharyngeal Gland Secretion as a Modifier of Aggressive Behavior in the Myrmicine Ant Manica rubida Abraham Hefetz, !'2 Christine Errard, I Alice Chambris, l and Alain Le Negrate ~ Accepted February 28, 1996; revisedApril 15, 1996 The role of postpharyngeal gland secretion in nestmate recognition was tested in Manica rubida. Behavioral tests comprised two consecutive encounters between five ants and their color-marked nestmate. The first encounter utilized an untreated ant constituting a control, whereas in the second encounter the marked ant was treated with postpharyngeal gland exudate. Scoring was done using an aggression index obtained by direct observation and an agitation index deduced from aflame-by-frame analysis of videotapes of the various tests. When the glandular secretion originated from an alien ant, the ants became very agitated and were aggressive toward their nestmate. When the exudate origi- nated from a nestmate, the ants generally remained calm, although their rates of self-grooming increased. KEY WORDS: postpharyngeal gland; nestmate recognition;aggressive behavior; agitationindex; Manica rubida; Formicidae. INTRODUCTION Nestmate recognition constitutes one of the most complex behaviors in ants. Generally speaking, it allows the cohesiveness of the ant colony and protects it from exploitation by conspecific alien ants. Much attention has been given in recent years to the chemical nature of the signals that are responsible for nestmate recognition, leading to the conclusion that these cues reside among the chemicals ' Labomtoired'Ethologie Experimentale et Compar~e, Universit~ Paris Nord, CNRS 2214, 93430 Villetaneuse, France. 2To whom correspondenceshould be addressed at Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel. 709 0892-755319610900-0709509.5010 9 1996 Plenum Publishing Corporation