Distribution of the abundances of CH₃CN as a function of the two indicators of evolution T_dust (top panel) and L∕M (bottom panel). The yellow points represent the five sources of Subsample II identified as early evolutionary stage, candidates HMSCs or very early HMPOs. The blue dashed line indicates the conservative threshold for abundances of methyl cyanide of 4 × 10⁻¹¹ (only HMSCs), while the gray area indicates the abundance range in which the sources are most likely HMSCs or very early HMPOs.