Preferential Brood Care in Artificially Mixed Acromyrmex Colonies

Here we tested the hypothesis of Holmes and Sherman (1983) that an individual that emerges in a mixed colony integrates the chemical signals of the social environment (allo- and conspecific) and acquires a mixed memory for future comparisons, a topic still unknown for Acromyrmex species. For this purpose, the interactions of workers with concolonial, conspecific and allospecific larvae were recorded over a period of 1 hour in two experimental groups of two Acromyrmex species (A. subterraneus brunneus and A. subterraneus molestans), with 10 replications in each experimental group, totaling 40 hours of recording. Five behaviours related to offspring care performed by A. subterraneus molestans and A. subterraneus brunneus workers were recorded: licking the larval body, carrying larvae into fungus sponge, ingesting faecal liquid, inserting hyphae on body of larvae, and scraping the larval mouthparts. The results indicate different levels of acceptance and rejection of concolonial, conspecific and allospecific larvae in A. subterraneus brunneus and A. subterraneus molestans workers. In conclusion, the data suggest that A. subterraneus molestans and A. subterraneus brunneus workers tend to prefer larvae of their own species, regardless of whether or not they are concolonial, thus confirming the hypothesis of Holmes and Sherman.