Honesty of Larval Begging Signals Covaries With Colony Kin Structure in Formica Ants

Abstract

Social insects live in highly complex societies with efficient communication systems. Begging is one display commonly used by offspring to signal their nutritional state, however begging behavior has received very little attention in social insects. Theory predicts that begging can be either an honest (i.e., honest-signaling strategy) or a dishonest (i.e., scrambling competition) signal of need, with dishonest signals expected to be more likely when relatedness within the group is low. To investigate the presence and honesty of begging, as well as the nature of the involved signals, we used a comparative approach with four species of the ant genus Formica known to differ in the degree of intra-colony relatedness. We investigated the behavior of starved and non-starved larvae of F. aquilonia, F. pressilabris (both low intra-colony relatedness), F. exsecta (intermediate relatedness), and F. fusca (high relatedness). In addition, we assessed the attraction of conspecific workers toward odors extracted from these two classes of larvae and analyzed the larval cuticular hydrocarbon profiles. We found that in F. fusca and F. exsecta, larvae signaled significantly more when starved. In contrast, larvae of F. aquilonia signaled significantly more when they were non-starved, while there was no significant difference in the behavior of starved vs. non-starved larvae in F. pressilabris. Our results show that workers were not preferentially attracted to the odor of starved larvae, and we also did not detect any differences between the cuticular hydrocarbon profiles of starved and non-starved larvae. Overall, this study demonstrates among species variation in larval hunger signaling in Formica ants, and encourages further studies to confirm the link between kin structure variation and the honesty of begging signals.

The evolution of eusociality: Kin selection theory, division of labour models, and evo-devo explanations

“…This then leads to a contextual shift of behaviours performed by individuals. For instance, if individuals have an evolved behavioural response to provide parental care when sensing the presence of larvae, then a heterochronous expression of parental care behaviours directed at siblings could be triggered by cues released from the larvae 150,[153][154][155][156] , such as larval begging behaviours [157][158][159][160] . As West-Eberhard highlights, the induction of helping could thus happen without any genetic change but as a side effect of a mutation affecting a behaviour or an environmental induction of a behaviour that is not directly related to helping 152 .…”

Brood recognition and discrimination in ants

“…Access to information about brood traits such as developmental stage, size, sex, maternity, caste and hunger level can help workers optimize their feeding behavior, for example in cases, where brood of different ages, sexes, or castes have different nutritional requirements (Brian 1981;Boomsma and Isaaks 1985;Cassill and Tschinkel 1996;Smith et al 2008b;Smith and Suarez 2010). Recognizing hungry larvae can help workers optimally allocate food (Brian and Abbott 1977;Cassill and Tschinkel 1999;Lopes et al 2005) and both behavioral and chemical cues have been implicated in larval begging (Le Masne 1953;Vowles 1955;Cassill and Tschinkel 1995;Creemers et al 2003;Kaptein et al 2005;Pegnier et al 2019). Importantly, since it is commonly assumed that queen-worker caste differentiation is modulated by differences in individual nutritional provisioning, workers should be able to adjust their feeding behavior according to larval caste to produce the polymodal size distribution of female castes observed in many species (Trible and Kronauer 2017).…”

The Scent of Ant Brood: Caste Differences in Surface Hydrocarbons of Formica exsecta Pupae

“…The precise role of these compounds remains unknown, but they may originate from the larval stage. Indeed, the monomethyl 7-MeC 29 , and other monomethylated-C 29 hydrocarbons, were present on larvae as well (Peignier et al 2019)(Table S2 in Supplementary Material). These were also found on newly emerged sexuals of F. exsecta, but not on mature ones (Martin et al 2014 S2 in Supplementary Material).…”

“…The adult chemical profile is very simple, consisting of four n-alkanes, which relate to task differences (Martin and Drijfhout 2009b), and four (Z)-9-alkenes, which have been found to act as nest-mate recognition cues (Martin et al 2008c(Martin et al , 2013. The surface chemistry of eggs (Helanterä and d'Ettorre 2014), and larvae (Peignier et al 2019) of F. exsecta have also been studied, but to our knowledge the surface chemistry of pupae remains uncharted. We characterize the surface chemistry of both sexual and worker pupae in this species, how it relates to the chemistry of adult workers, and explore the qualitative and quantitative differences among them.…”

“…Peignier et al 2019) of F. exsecta, but were not consistently present on adult workers, or on newly emerged or mature sexuals of this species(Martin et al 2014) (Table…”