Food preferences displayed by foraging insects are important from a fundamental perspective and in pest control. We studied the preference of an invasive wasp, V. germanica, for protein foods in field conditions. Preferences were evaluated by placing baits in a paired design in different habitats and analyzing wasp visits, using a Bayesian approach to the Thurstone model. V. germanica workers display a clear rating of preferences, but were affected by the presence of competitors at the bait. These results contribute knowledge aimed at toxic baiting protocols for this wasp and suggest that food choice is a complex process subject to the influence of diverse factors. We emphasize the importance of on-site paired comparisons in preference studies to fully understand the drivers of food choice by insects. ; Fil: Pereira, Ana Julia. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Patagonia Norte. Estacion Experimental Agropecuaria San Carlos de Bariloche. Laboratorio de Ecologia de Insectos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina ; Fil: Masciocchi, Maité. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Patagonia Norte. Estacion Experimental Agropecuaria San Carlos de Bariloche. Laboratorio de Ecologia de Insectos; Argentina ; Fil: Bruzzone, Octavio Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Patagonia Norte. Estacion Experimental Agropecuaria San Carlos de Bariloche. Laboratorio de Ecologia de Insectos; Argentina ; Fil: Corley, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Patagonia Norte. Estacion Experimental Agropecuaria San Carlos de Bariloche. Laboratorio de Ecologia de Insectos; Argentina