Fire Ants Feed Their Nestmates with Their Own Venom

Abstract

Venom secretion is widely used by ants for disease control and generally used as an external surface disinfectant. Here we report evidence that Solenopsis invicta feed their nestmates with their own venom. Venom alkaloids at concentration levels that were reported to be effective against various pathogens were found in crops and midguts of ants. Venom alkaloids were found in midguts of the larvae, indicating that trophallaxis must be involved in the transfer of venom, since larvae do not produce alkaloids and they depend on workers to be fed. After the mating flight, the female alates shed their wings, burrow into the soil and start new colonies. The new queen provided alkaloids to her first batch of larvae in the new colony. Since the crops of female alates contain venom alkaloids donated from their nestmate workers, the transfer of worker alkaloids to new generation occurred. After minim adult workers emerged, they took the role in providing venom to the larvae in the colony. Minim adults eventually died out and the normal workers become the venom donors in the colony. Although other functions may be possible, considering the well known antimicrobial property of venom alkaloids and their detected concentration levels, venom in the digestive system is most likely used as an internal antibiotic by fire ants.

Keywords: Social insect, crops, midguts, venom alkaloids, internal medication