Black fly plague and its mighty bite spreads across Spain

black fly (Simulium erythrocephalum) is not an invasive species in Spain, but rather an autochthonous insect of Iberian ecosystems, but has been experiencing unprecedented peaks in its populations for several years. At least in the regions of Madrid, Catalonia, Valencia, Murcia, Aragon and Andalusia, this is the general perception that these flies have become a veritable plague attacking both humans and animals.

In Madrid alone, from 2015 to 2019, health services treated more than 300,000 people suffering from its bite. According to health sources, more than 20,000 patients are affected in Zaragoza each year, while ten years ago this number did not exceed 4,500.

And the bite of the black fly is particularly intense. What this insect does more than sting is biting the skin., leaves a visible bruise that can last for several days to a week. Many residents of the affected towns had to go to the emergency room, complaining of large swellings, dermatitis, and severe itching.

But not just people. Pets and farm animals are also affected by the black fly. Species that seem to be favored by heat.


It mainly attacks sheep, cattle, horses and goats, but also dogs and other pets. These insects form a large cloud surrounding the animal and will not stop harassing and biting it, so many farmers have had to change the time they take their animals outside to avoid this pest as much as possible. Nobody seems safe. Veterinarians also had extra work for several summers.

This annoying insect is very small, from 3 to 6 mm, more like a wasp.

Apparently, due to the proliferation inadequate cleaning of river bedsIt is the product of products that have been incarcerated for months due to the coronavirus pandemic, according to multiple media outlets in the affected areas.

This black fly lays its larvae on vegetation that is in contact with fresh water. These insects have multiplied because the cleaning of these channels could not be done correctly.

In addition, high temperatures also favored early hatching. The gradual disappearance of its predators: swallows, gliders and batsInsecticidal species that need to be protected to keep such nuisance species away.

Its bite is more secretive than a mosquito. It supports the legs as little as possible on the skin so that it is unnoticeable. It injects a stronger anesthetic than mosquitoes and an anticoagulant to make the blood more fluid. We don’t realize it stings us until a good time later.


The bite is quite inflamed with a red spot in the center. In these cases, it is best to apply ice and go to the emergency room if there are signs of an allergic reaction (see suggestions below).

According to the Spanish Society of Emergency Medicine (SEMES), the bite, although painful, will cause an inflammation that does not pose any risk of disease transmission.

In Madrid, with the arrival of high temperatures, a few days ago many residents warned of the spread of black flies. A walk outdoors in certain areas can turn into torment due to the large number of black flies returning to populate the perimeter of the capital once again.

So already in 2020 the City Council carried out a major fumigation in the Manzanares River to eradicate this insect, but the problem seems to have resurfaced this year.


The same thing is happening in Catalonia. Ebro’s (Copate) Environmental Policy Consortium started the first treatment against black fly plague in February of this year. last part of the Ebro riverAfter last year, this action showed its effectiveness.

This organization has a budget of 1.3 million euros to combat black flies and mosquitoes. Half is provided by the Generalitat, the rest by the Tarragona Provincial Council and the municipalities of the Delta de l’Ebre.

1º How can I prevent stinging?

-Wear long and light clothes

– Do not spend much time in rivers or reservoirs

-Install mosquito net in your house

-Prevents water accumulation

-Use flying insect repellents

2. What are the symptoms?

Severe pain in the affected area

-Central red and bleeding spot

– Inflammation of the affected area

-Itching

-Swelling or blotchiness around the affected area

3º What is the treatment?

-Clean and disinfect the affected area with an antiseptic.

-Apply cold

– Don’t even think about scratching, you’ll only make it worse

– The product soothes bites

4. Consult a health center or your specialist

SEMES website on blackfly: https://www.semes.org/semes-divulgacion/picadura-de-mosca-negra/

You may be interested in: Climate change triggers pests that already destroy 40% of crops

Source: Informacion

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