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

## TL;DR

This paper reports the first discovery of the fly Carnus hemapterus in the Southern Hemisphere, found in bird nestlings in Argentina.

## Contribution

The first record of Carnus hemapterus in the Southern Hemisphere and a new host species, Chimango caracara, are documented.

## Key findings

- Carnus hemapterus was found in Argentina, marking its first appearance in the Southern Hemisphere.
- The fly was observed parasitizing nestlings of the American kestrel and the Chimango caracara.
- The presence of the fly in bird nests may have broader ecological and physiological impacts.

## Abstract

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.

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•First record of bird ectoparasite fly, Carnus hemapterus in the entire Southern Hemisphere.•C. hemapterus were found parasitizing nestlings of wild birds of prey in Argentina.•The American kestrel has already been recorded as a host in North America.•The Chimango caracara represents a new host species for this ectoparasite fly.•The presence of this fly can be underestimated in wild birds below the equator.

First record of bird ectoparasite fly, Carnus hemapterus in the entire Southern Hemisphere.

C. hemapterus were found parasitizing nestlings of wild birds of prey in Argentina.

The American kestrel has already been recorded as a host in North America.

The Chimango caracara represents a new host species for this ectoparasite fly.

The presence of this fly can be underestimated in wild birds below the equator.