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Gadfly.

New horsefly species found in the fauna of Finland

With the addition of the striped horsefly to Finland’s fauna, there are now 39 horsefly species in Finland.

Last week, a group of researchers from the University of Eastern Finland, the Finnish Museum of Natural History and the Zoological Museum of the University of Turku discovered a horsefly species that hasn’t been recorded in Finland before. The species was discovered near Finland’s southernmost city Hanko, in the surroundings of Tvärminne Zoological Station. 

The newly found horsefly, Hybomitra expollicata, belongs to the relatively large Hybomitra species, many of which are very similar to each other. However, the species is easy to distinguish from other members of its genus because it has a distinctive light colour, longitudinal stripes in the back of its body, and a steadily narrowing abdomen. As the name of the species in English is striped horsefly, owing to the longitudinal stripes in the back of its body, its Finnish name with a similar meaning could be “juovapaarma”.

The striped horsefly is particular about its habitat, thriving in coastal brackish marshes and wetlands. In Europe, the striped horsefly is mainly found in tidal marshlands and river estuaries along the coast of the Atlantic and the Mediterranean. Closest to Finland, the species is found in Skåne and Öland in southern Sweden. However, due to the drainage and development of coastal wetlands, the striped horsefly is endangered in most parts of Western Europe and in Sweden, too, it is considered a vulnerable species.

In Finland, the striped horsefly has a stable population at least in the surroundings of Tvärminne, since the researchers discovered several individuals in one day. It is possible that the species has spread to Finland recently, because the horsefly species in Hanko, and especially in the surroundings of the zoological station, are well documented and it is unlikely that such a distinctive species would have been missed in the past. It is possible that the striped horsefly is found also in other favourable locations along the southern coast of Finland.

With the addition of the striped horsefly to Finland’s fauna, there are now 39 horsefly species in Finland.

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Profile picture: Jaakko Pohjoismäki

Jaakko Pohjoismäki

Senior Researcher

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