The behavioural effects of sublethal insecticide exposure towards minor workers are the main determinants of insecticide activity as ant baits and should be targeted in developing such compounds. © 2016 Society of Chemical Industry.

Social insects can live in densely populated colonies where mortality risks are increased by inter-individual transmission of pathogens. Thus, diverse strategies are employed against such infection risks, including the display of sophisticated behavioural traits. Considering that the waste of the leaf-cutting ant contains pathogens, worker ants that tend the fungus garden -here called fungus garden workers -should exhibit avoidance behaviour toward midden workers to minimize contamination of the fungus garden. We studied the behaviour of garden workers when confronted with midden and forager workers in colonies of Atta sexdens (Linnaeus, 1758). Eight colonies were used: in four colonies, the midden was inoculated with spores of the weed fungus Escovopsis weberi (Muchovej and Della Lucia, 1990), and in the other four colonies there was no artificial contamination. Grooming, self-grooming, inspection, immobilization and aggression behaviours were quantified. Additionally, we checked for fungal contaminants on the body surfaces of midden and garden workers from non-inoculated colonies. Garden workers displayed more intense behaviours (grooming, inspection and immobilization) toward midden workers than toward foragers; these behaviours did not differ between Escovopsis-inoculated and non-inoculated colonies. No antagonist behaviour was displayed by garden workers toward midden or forager workers independently of the inoculation treatment. Eight fungus species were isolated from the midden and garden workers, including Trichoderma sp., a probable antagonist of the fungus garden. Garden workers of A. sexdens discriminate against midden workers; however, a previous hypothesis that pathogens from the midden induce the aggressiveness of internal workers is not supported by our study.

No abstract

BACKGROUND: Animal personality refers to behavioral consistency and propensity. In social insects, little is known about the interplay between colony personality and colony foraging. This study aimed to assess personality traits among colonies of the leaf-cutting ants Acromyrmex subterraneus subterraneus and Acromyrmex subterraneus molestans and examine their behavioral consistency when provided with a toxic substrate, nasturtium leaves [Tropaeolum majus L. (Tropaeolaceae)], with potential as a management tool against these pest species. The association between colony behavioral traits and fungus garden growth was also examined, and thus the efficacy of the colony suppression. RESULTS: Behavioral variation was higher between colonies than between subspecies. Behavioral traits were correlated before and after exposure to resource-mediated stress in both subspecies, indicating the existence of behavioral syndrome. The dimensions that contributed most to colony personality (activity, aggressiveness, and boldness) are directly related to colony resource searching and foraging. However, these dimensions diverged in their contribution before and after exposure to nasturtium. Colony activity was the major determinant of fungus garden growth, which is probably a consequence of its relationship with foraging behaviors and maintenance of the fungus garden. CONCLUSION: As the personality of a colony is unequally defined by its constituent castes, the relationship and network of interactions are determinants of foraging behaviors with relevant consequences for colony suppression using toxic foraging substrates that impair these relationships and interactions, as nasturtium leaves do. Therefore, it is plausible to say that resource-mediated stress affects colonies personality exhibiting control potential against these species.