Nestmate recognition, the ability to recognize a nestmate from a non-nestmate, is critical to the ecological success of eusocial insects. Although cuticular hydrocarbons are thought to serve as cues in nestmate recognition, little is known about how specific hydrocarbons vary between colonies and which ones are responsible for evoking nestmate recognition behaviors. The aim of my study was, using the ant Formica argentea, to investigate cuticular hydrocarbons in great detail by addressing the following questions: (1) What cuticular hydrocarbons are present? (2) Can any one group of compounds statistically classify workers by nest? (3) Which structural classes of hydrocarbons evoke a nestmate recognition response? (4) Do increased differences in cuticular hydrocarbon profiles predict aggression? (5) How do different structural classes of hydrocarbons change with time? After chemical analyses I found that the cuticular hydrocarbon profile of F. argentea workers contain a mixture of n-alkanes, alkenes, and methyl-alkanes which stay fairly constant within a nest but vary in relative proportion between nests. Additionally, using the only the C₂₉ methyl-alkanes in a hierarchical cluster analysis was enough to correctly classify workers by nest. Behavioral experiments demonstrated that both methyl-alkanes and alkenes increased aggression in workers while n-alkanes did not. Differences in cuticular hydrocarbon profiles between pairs were a good predictor of aggression with differences between particular methyl-alkanes weighing more heavily on the statistical analysis. When kept in a uniform environment the average relative proportions n-alkanes, alkenes, and methyl-alkanes, varied with time, while the relative proportion of the C₂₉ methyl-alkanes remained constant. These finding indicate that all structural classes of cuticular hydrocarbons should not be grouped together or treated equally in nestmate recognition analyses. This study improves our understanding of nestmate recognition and cuticular hydrocarbon profiles in eusocial insects.