<p>Mutualist ants have been shown to influence the morphological evolution of trophobiotic root mealybugs in interesting ways. This study evaluates the morphology of setae across all described root mealybugs (Hemiptera: Rhizoecidae, Xenococcidae) and assesses whether there is a relationship between the types of setae represented in a species and their status as an obligate ant mutualist (i.e., associated vs. free-living). Myrmecophilous root mealybugs are indeed found to have unusual setae in addition to the simple flagellate body setae that all species possess, and such atypical setae are a rarity among free-living species. Several of the atypical setal forms are strictly found in myrmecophilic species. Clavate and spiniform setae are distributed among both myrmecophiles and free-living species but, of the two, only clavate setae were found to have a significant relationship with ant association. The forms of setae associated with myrmecophily, specifically sensory-tipped setae, show some convergence between members of Rhizoecidae and Xenococcidae, and furthermore even among the associates of herdsmen ants from the family Pseudococcidae. Convergent traits represent similarity due to shared ecology rather than shared history, but atypical setae have lent justification for the establishment of multiple genera in the family Rhizoecidae, suggesting that myrmecophily may have a confounding influence on root mealybug taxonomy. We describe a new species, <i>Williamsrhizoecus hisopo</i> Schneider &amp; LaPolla sp. nov., discovered in association with <i>Acropyga exsanguis</i> from Panama and discuss the potential significance of unusual setae in the context of ant association.</p>