Always under foot: Tetramorium immigrans (Hymenoptera: Formicidae), a review

The pavement ant Tetramorium immigrans is a widespread and prevalent species in temperate urban areas. Yet, despite this commonness, it was only in 2017 that T. immigrans was differentiated from other members of its complex which had largely been regarded under the umbrella species ???T. caespitum". As a result, past literature treats multiple species synonymously while current papers continue to cite T. caespitum findings as authoritative on T. immigrans. This review delineates what is known about T. immigrans while placing this information in a natural history context where possible. Given the state of our knowledge, it is likely a semi-arid open-field specialist which has multiple fortuitous "preadaptations" to human disturbance, and which has spread across Europe and North America in tight synanthropy as a result. It recruits rapidly to food, whereby making use of spotty urban resources, and is comparatively self-compatible as a species, allowing it to live at high densities where it is the dominant ant. However, it appears to have a comparatively mild impact on both human activity and biodiversity. Some future avenues of research are discussed concerning this widely distributed ant which is a convenient and interesting study system.