1 Nestmate Recognition in the Ant Odontomachus bauri (Hymenoptera: Formicidae) by C. Sainz-Borgo 1* , A. Cabrera 2 & J. V. Hernández 1 ABSTRACT In order to study the nestmate recognition signal in Odontomachus bauri, behavioral tests and chemical analyses of the mandibular (MG) and post- pharyngeal gland (PPG) compounds were performed. Behavioral bioassays consisted of placing two workers (a nestmate and an alien) on the foraging area in the surroundings of the O. bauri nest; three types of treatments were applied. hese were: whole bodies, body parts and gland extracts. In each treatment, the ant behavior was quantiied. Chemical analyses of MG volatiles were performed using the headspace-solid phase microextraction technique and PPG hydrocarbons were analyzed by the solid sample technique. hen both were analyzed by gas chromatography-mass spectrometry. Workers recog- nized conspeciics and body parts from other colonies as aliens, showing that recognition signals are found over the whole body. Dummies impregnated with MG and PPG extracts were recognized as aliens, but the thorax with MG alien extract received more attacks than the thorax with the nestmate extract. Chemical analyses showed that MG volatiles have intercolonial variation. Most of the behavioral and chemical evidence show that both MG volatiles are involved in the nestmate recognition system. Key Words: HS-SPME, Mandibular gland, Nestmate recognition, Od- ontomachus bauri, Postpharyngeal gland. INTRODUCTION Nestmate recognition consists of the ability of social insects to distin- guish between the individuals of their own colony and non-nestmates. hat 1 Laboratorio de Ecología Química del Comportamiento, Departamento de Biología de Organismos, 2 Departamento de Química; Universidad Simón Bolívar, Apartado 89000, Caracas 1080A, Venezuela *Corresponding author. e-mail: cristinasainzb@gmail.com