﻿AbstractThere are only twoAphaenogasterspecies from thesubterraneagroup in the western Mediterranean:A.ichnusaSantschi, 1925, from south-western Europe, andA.subterranea(Latreille, 1798), also occurring in central and eastern Europe. Historically, the two species have been widely misunderstood:A.ichnusawas long considered a Sardinian endemic subspecies ofA.subterranea, while its continental populations were misidentified asA.subterraneas. str. Recently,A.ichnusawas elevated to species rank and its worker caste was redescribed with that ofA.subterranea, allowing for their correct identification. Yet their distribution was documented in detail only for France and Sardinia. Furthermore, no morphological characters were described to distinguish the males and queens of the two species. By investigating private and museum collections, 276 new records ofA.ichnusaare provided here and 154 ofA.subterraneafrom the western Mediterranean. Additionally, qualitative and quantitative morphological characters were combined to identify their males and queens. We present the new southernmost, easternmost, and westernmost distribution limits forA.ichnusa. Based on our results, this species is widely distributed in Italy and Catalonia (Spain), also occurring on several Mediterranean islands, avoiding areas with continental climate and high altitudes. Sicily is the only island to host the less thermophilousA.subterranea, which otherwise extends westward to Galicia (Spain). Sympatric occurrence is not rare along the contact zone. Additional natural history observations are reported regarding foraging habits, associated myrmecophiles, habitat preferences, and colony structure in the two species.