The identification of Cx. stigmatosoma and Cx. thriambus is sometimes confused in Mexico. Intraspecific differences in spiracular apodeme on Cx. stigmatosoma larvae and chaetoaxy on siphon of Cx. thriambus are reported and illustrated here. Based on specimens from recent collections, we include distribution, ecologic, medical importance, and taxonomic notes, and additional collection records in Mexico are documented for both species.