Which feature helps identify an adult fire ant?

Identifying an adult fire ant is primarily done by recognizing its distinctive coloration, which varies from reddish to dark brown. This characteristic coloration helps distinguish fire ants from other species that may appear similar but possess different colorations. The reddish to dark brown hue is a reliable visual cue for pest control professionals or anyone attempting to identify these ants in the field.

While other features listed in the choices contribute to the identification of different ant species, they do not specifically pertain to fire ants. For instance, the presence of two nodes could apply to various ant species and therefore is not exclusive to fire ants. Similarly, the light tan color is more characteristic of other ant species and not representative of the fire ant’s typical coloration. The mention of a silvery shine does not align with the fire ant's distinct appearance either, as they lack such a reflective feature. Thus, the reddish to dark brown color is the most defining and accurate characteristic when specifically identifying adult fire ants.