The first record of the ectoparasite fly Carnus hemapterus for the Southern Hemisphere

The genus Carnus (family Carnidae, Order Diptera) comprises five species of small-bodied and blood-sucking flies that parasitize nestlings of wild bird species. Almost all species in this genus are restrictely distributed across different continents in the Northern Hemisphere, particularly Carnus hemapterus, which is a widespread ectoparasite of many bird species. Here, we report C. hemapterus parasitizing wild birds in central Argentina, resulting in the first record for the species in the entire Southern Hemisphere. Individual flies of C. hemapterus were found in nestlings of two bird of prey species, the American kestrel, already recorded as a host of C. hemapterus in North America, and the Chimango caracara, a new host species for this ectoparasite. Consistent with the species' life cycle, flies were observed only in nestlings but not in adult individuals captured in the same breeding areas. Besides the plausible reasons that could explain this new report, it significantly updates the global distribution for this ectoparasite taxon. Therefore, this record should draw the attention to ornithologists and parasitologists from large regions of the global South, which include some of the most important avian biodiversity host-spots, to this new ectoparasite-host interaction, which may affect a significant number of bird species and warrants investigation of its physiological and ecological impacts. Furthermore, beyond its role as an avian ectoparasite, C. hemapterus is involved in complex interespecific interactions, serving as a host for parasitoids and participating in multitrophic food webs within bird nests, which clearly warrant further research.