The ants (Hymenoptera: Formicidae) of Iceland
The native terrestrial biota of Iceland required long oceanic journeys to colonize the island. Human colonization of Iceland, however, has allowed many less vagile species, such as ants, to reach the island. We compiled published, unpublished, and new records of ants from Iceland and evaluated the probable origin and current status of each species. We analyzed 565 records compiled by the Icelandic Institute of Natural History (1974-2020) and 84 new records (2019-2023) representing 25 species. Only five species were found living outdoors: Hypoponera ergatandria (507x indoors and 9x outdoors, mostly in geothermal areas), Lasius niger (24x indoors and 12x outdoors away from heated buildings), Hypoponera eduardi (5x only in geothermal areas), Lasius platythorax (1x near a small greenhouse and 1x in imported plant material), and Myrmica rubra (1x in an urban garden). Three ant species were exclusively found inhabiting heated buildings: Monomorium pharaonis (41x), Tapinoma melanocephalum (10x), and Monomorium nr. pharaonis (3x). Records of the remaining 17 species all appear to be based on temporary infestations, found on recently imported plant material. Previous records from Iceland of Hypoponera punctatissima appear to be based on misidentifications. Although it is possible that some ants were present before human arrival, all 25 ant species may have arrived accompanying humans. It remains to be seen whether any of these ant species are having or will have a significant impact on the native Icelandic biota. The arrival of Myrmica rubra in Iceland is particularly worrisome, given the impact this species is having in other high latitude areas it has invaded.