Abstract
Task allocation ensures a high level of organization within social insect colonies. Workers reveal their task assignment through cuticular hydrocarbon (CHC) signals. The source and chemical composition of these signals are largely unknown. We ask whether task recognition signals are located on particular body parts of workers of Australian meat ants (Iridomyrmex purpureus). We analysed the CHC profile on the antennae, legs and abdomens of workers engaged in different tasks. Discriminant analysis showed that the leg profile is the best indicator of task identification. Behavioural assays confirmed this finding: workers typically reacted differently to non-nestmates engaged in different tasks, but not if the CHCs on the legs of their opponents were removed by a solvent. Lasso and Elastic-Net Regularized Generalized Linear Model (GLMNET) revealed which CHC components show the highest correlation in task and nestmate recognition, suggesting that social insects can simultaneously convey different CHC signals on different body parts, thereby allowing efficient signaling and signal perception.
Highlights
Social insect colonies are self-organized, with social cohesion achieved by individual workers making simple decisions based on their interactions with other workers (Sachs, 2004)
Following Wang et al (2016), who showed that workers of I. pupureus paid more attention to the antennae of non-nestmates and the legs of nest-mate workers, we investigate the role of location specific cuticular hydrocarbon (CHC) in signaling task allocation in I. purpureus
The chemical profiles of CHCs on the antennae, legs and abdomens differ according to the task of the worker (Figures 1A–C), but the legs provide qualitatively greater task discrimination accuracy (81.4% correct classification) than either the antennae (71.7% correct classification) or abdomens (69.5% correct classification)
Summary
Social insect colonies are self-organized, with social cohesion achieved by individual workers making simple decisions based on their interactions with other workers (Sachs, 2004). Cuticular hydrocarbons (CHCs) are the most abundant chemicals on the surface of ants, and play key roles in several communication contexts, including nestmate recognition (Martin et al, 2008; van Wilgenburg et al, 2010), task recognition (Wagner et al, 1998; Greene and Gordon, 2003; Nascimento et al, 2013), trail marking (Hölldobler et al, 2004), recruitment of foragers (Greene and Gordon, 2003), and queen viability and fertility signals (Cuvillier-Hot et al, 2004; Lommelen et al, 2006; van Oystaeyen et al, 2014). The role of CHCs in communicating tasks is poorly understood
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