They are only two to six millimeters in size and they resemble harmless house flies, but their bites are very unpleasant: black flies.
According to a study published in the journal “Science of the Total Environment” by researchers at Goethe University and the Senckenberg Biodiversity and Climate Research Center in Frankfurt, the insects could soon become significantly more common in this country.
Future higher temperatures could “lead to shortened development times, more generations per year and thus an overall more frequent occurrence of black flies,” the research team explained.
Black flies can transmit pathogens
According to researchers, the flyable and predominantly black insects are “pool suckers”: female animals rasp the host’s skin with sharp “teeth” and then ingest the drop of blood that forms there.
Due to the anticoagulant and anesthetic substances introduced into the wound by the mosquitoes, the bites could trigger serious allergic reactions, explained Sven Klimpel from the University of Frankfurt. “Black flies are also vector-competent, meaning they are able to transmit pathogens that cause infectious diseases through their bite,” said Klimpel.
The best-known pathogen transmitted by black flies is the nematode Onchocerca volvulus, which is native to the African continent and can cause so-called river blindness. According to the World Health Organization (WHO), more than 1.15 million people worldwide have suffered vision loss as a result of the disease.
Species divided into three groups
About 98 percent of the 2,000 black fly species found on all continents – with the exception of Antarctica – feed on blood, said co-author Sarah Cunze from the University of Frankfurt. So far, 57 species of black flies have been discovered in Germany. Using 1,526 data sets from Hesse, North Rhine-Westphalia, Rhineland-Palatinate and Saxony, the researchers divided the twelve most common species native there into three biogeographic groups: “Species that live on the headwaters of water, species that are widespread across different landscapes and lowland species” said Cunze.
In their current study, the researchers predict different developments for the three groups: The group of species with a distribution focus in the upper reaches of water is considered to be potentially endangered due to rising temperatures and increasing chemical pollution of the waters. Lowland species, on the other hand, were characterized by a higher tolerance to man-made changes and could become more common in the future.
They also include medically important species. They are characterized by a particularly aggressive stinging behavior towards mammals and humans and often occur in very large numbers. Future higher temperatures could lead to shortened development times, more generations per year and thus an overall more frequent occurrence of black flies, says Cunze.
In further work, the research team would like to use laboratory tests to clarify the extent to which blackfly species are able to transmit certain pathogens of infectious diseases under the conditions prevailing in Europe.
