Maternal care and offspring begging in social insects: chemical signalling, hormonal regulation and evolution

Posthatching maternal care such as food provisioning and protection has evolved several times in insects, allowing offspring (larvae, nymphs) to interact with their mothers and potentially influence their investment. The evolutionary conflict over the duration and amount of parental care is thought to promote the evolution of offspring begging behaviours either as honest signals of need or as competitive signals with the potential to manipulate parents into investing more. In most social insects, parental care is not obligatory and may represent a less derived state than in vertebrate systems making them more appropriate to test ancestral conditions for the evolution of begging signals. Here, we review forms of maternal care in insects ranging from protection to food provisioning and evidence of offspring begging behaviours influencing maternal care, including condition-dependent chemical cues produced by offspring that may turn out to be solicitation pheromones. Since behavioural parenteoffspring interactions are embedded in the reproductive and developmental physiology of mother and offspring, we stress the need for behavioural studies to be complemented by physiological measurements which will allow us to understand better the nature of conflict resolution. We propose a hypothetical mechanism of maternal care regulation by direct internal chemical signals (i.e. hormones) and indirect external chemical signals (i.e. solicitation pheromones) influencing maternal reproductive physiology and future reproduction. Social insect species and the integrated study of behavioural interactions and physiological/reproductive consequences may represent promising new experimental systems for direct tests of the evolution of begging signals, complementing current research on parenteoffspring conflict.