Effect of continuous exposure to foreign cuticular signature in nestmate recognition system of Argentine ants (Linepithema humile)

Nestmate recognition is a ubiquitous phenomenon in social insects as a means to prevent undesired individuals from entering to the rich nest resources. Social insects often use cuticular hydrocarbon odor cues as colony-specific signature, and they are believed to learn the chemical signatures that identify nestmates through social experiences. One of these social experiences occurs at the very beginning of an ant’s adult life, immediately after its emergence from pupal exuvia. During this period, ants may imprint on the odors of other ants or nesting materials around them, thus forming an internal, neural concept of the types of odors that define the colony. Thus, we hypothesized that if young adult ants (callows) are exposed to particular hydrocarbon cues, they will display reduced aggression toward the same odors at adulthood. To test this hypothesis, we performed an experiment in which Argentine ant workers (callow and older) were continuously exposed to a suite of cuticular hydrocarbons obtained from a foreign colony. Behavioral bioassays revealed that the exposed ants displayed a reduced level of aggression toward the ants from the foreign colony while the control ants remained highly aggressive to them. These data demonstrate that there is plasticity in the nestmate recognition mechanism. At the same time, this plasticity illustrates a potential weakness in the nestmate recognition system, which may be exploited by other organism, such as social parasites.