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Close-up of a blackfly

Photo: Dorian D. Doerge / Senckenberg Biodiversity and Climate Research Center / dpa

Black flies are only two to six millimeters long, but their bites are unpleasant.

In the future, they could occur much more frequently in Germany, write researchers from Frankfurt's Goethe University and the Senckenberg Biodiversity and Climate Research Center in the journal "Science of the Total Environment".

Higher temperatures could “lead to shortened development times, more generations per year and thus an overall more frequent occurrence of black flies,” explained the research team.

Unlike ordinary mosquitoes, the predominantly black insects are “pool suckers”: female animals, like ticks, rasp the skin of their host with sharp mouthparts.

They introduce anticoagulant and anesthetic substances into the wound.

These could trigger serious allergic reactions in people, says parasitologist Sven Klimpel from the University of Frankfurt.

“Black flies are also vector-competent, meaning they are able to transmit pathogens that cause infectious diseases.”

57 different species

The best-known pathogen transmitted by black flies is a nematode native to Africa that can cause river blindness, it said.

According to the World Health Organization (WHO), more than 1.15 million people worldwide have suffered vision loss as a result of the disease.

The researchers now want to use further laboratory tests to determine whether black flies can also transmit pathogens under the conditions in Europe.

About 98 percent of the 2,000 blackfly species feed on blood, says co-author Sarah Cunze from the University of Frankfurt.

So far 57 species have been discovered in Germany.

Using more than a thousand data sets from Hesse, North Rhine-Westphalia, Rhineland-Palatinate and Saxony, the researchers divided the twelve most common native species into three biogeographical groups: species that live on headwaters, species that are widespread across different landscapes, and lowland species.

In their current study, the researchers predict different developments for the three groups: species that live primarily in the upper reaches of water are considered to be potentially endangered due to rising temperatures and increasing chemical pollution of the waters.

Lowland species, on the other hand, are more tolerant of man-made changes and could increase in number.

They also include medically important species.

They are characterized by aggressive biting behavior towards mammals and humans and often occur in very large numbers.

Bite or sting?

It is often discussed whether animals such as black flies or ticks bite or sting.

Since they open the skin with their mouthparts and then suck up the blood with a kind of proboscis, both names are conceivable.

After discussions with experts, we decided to write about biting.