Social insect colonies contain attractive resources. Colony members defend their colony integrity and exclude parasites by discriminating between the cuticular chemical profiles of nestmates and non-nestmates. Obligate social parasites trick their hosts about their chemical identity via chemical insignificance and/or mimicry of cuticular profiles (Lenoir et al. 2001; Bagnères & Lorenzi 2010). With few exceptions (e.g., Lorenzi et al., 2007, 2011), what facultative social parasites do to trick their hosts is largely unexplored. We analysed the chemical strategies of integration in Polistes nimphus facultative social-parasites of paper wasps by simulating nest usurpation in lab. Before host-brood emergence, we cut each paper-nest into two parts and assigned a half-nest to the original foundress and the other half to a facultative social parasites. After four days in the half nests, we removed foundresses and social parasites from their half-nests. When host workers emerged from half-nests, we tested their ability to discriminate between their foundresses and their usurpers and then we analysed the chemical profiles of foundresses, facultative social parasites and their half-nests. Behavioural tests and chemical analyses on the two half-nests document that facultative social parasites trick their hosts successfully about their chemical identity and show that they trick their hosts by overmarking. Facultative social parasites deposit their own odors on nest paper, where there are already the odors of original foundresses. Emerging workers use the odors deposited on nest paper as a reference to recognize colony members. Therefore host workers in parasitized half-nests learn multiple odors and accept their foundresses and their facultative social parasites as colony members. Our results highlight that facultative social parasites get tolerance and integration in host colonies by means of overmarking, a chemical strategy common in species other than social insects but rarely used by obligate social parasites.
Facultative social parasites in paper wasps overcome host detection by overmarking
LORENZI, Maria Cristina;
2012-01-01
Abstract
Social insect colonies contain attractive resources. Colony members defend their colony integrity and exclude parasites by discriminating between the cuticular chemical profiles of nestmates and non-nestmates. Obligate social parasites trick their hosts about their chemical identity via chemical insignificance and/or mimicry of cuticular profiles (Lenoir et al. 2001; Bagnères & Lorenzi 2010). With few exceptions (e.g., Lorenzi et al., 2007, 2011), what facultative social parasites do to trick their hosts is largely unexplored. We analysed the chemical strategies of integration in Polistes nimphus facultative social-parasites of paper wasps by simulating nest usurpation in lab. Before host-brood emergence, we cut each paper-nest into two parts and assigned a half-nest to the original foundress and the other half to a facultative social parasites. After four days in the half nests, we removed foundresses and social parasites from their half-nests. When host workers emerged from half-nests, we tested their ability to discriminate between their foundresses and their usurpers and then we analysed the chemical profiles of foundresses, facultative social parasites and their half-nests. Behavioural tests and chemical analyses on the two half-nests document that facultative social parasites trick their hosts successfully about their chemical identity and show that they trick their hosts by overmarking. Facultative social parasites deposit their own odors on nest paper, where there are already the odors of original foundresses. Emerging workers use the odors deposited on nest paper as a reference to recognize colony members. Therefore host workers in parasitized half-nests learn multiple odors and accept their foundresses and their facultative social parasites as colony members. Our results highlight that facultative social parasites get tolerance and integration in host colonies by means of overmarking, a chemical strategy common in species other than social insects but rarely used by obligate social parasites.
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