What is a key characteristic of Acrobat Ants?

Acrobat Ants are indeed characterized by their heart-shaped abdomen, which is one of their most distinctive features. This characteristic helps to identify them, especially when observing their behavior and physical appearance. The heart-shaped structure of their abdomen can be seen when they are viewed from above or when they are in a defensive posture, raising their abdomens over their thoraxes.

The other options highlight aspects that may not accurately describe the behavior or characteristics of Acrobat Ants. For instance, while they can have multiple sizes of workers, that trait is not exclusive to Acrobat Ants among ant species. Similarly, while nesting locations can vary, Acrobat Ants are not known to exclusively occupy grassy areas, as they will also nest in wood and other substrates. The notion that they do not bite when threatened is misleading as they do possess the capability to bite as a defense mechanism if provoked.