Black flies are found all over the world and there are about 50 species in the local latitudes that humans and animals attack to get their blood. The annoying suckers are usually not noticed, but caution is advised, especially in the vicinity of flowing water such as rivers and streams. Here they are usually recognized because they usually appear in swarms. The stings are usually noticeable through itching, for which the female black fly opens the skin with her saber-toothed mouthpart and then sucks up the blood that she needs for her eggs.


  • small, black, squat insects
  • become up to 6 mm long
  • about 1770 species worldwide
  • in local latitudes about 50 species
  • only the females attack animals and humans, biting the skin and sucking blood
  • they need this for the production of eggs
  • the male mosquitoes suck plant sap
  • mostly occur in flowing waters
  • live in a swarm
  • each female mosquito can lay up to 250 eggs in spring


Black flies stay mostly in the lowlands where there are flowing waters. Because unlike mosquitoes, which prefer stagnant water, black flies lay their eggs on plants that are near running water, where the larvae then develop. The mosquitoes mainly prefer grazing animals as hosts, but especially in spring, when the larvae have hatched en masse, they also fly to humans and pets for blood supply if they are close to a swarm.


Especially in spring, near a river or stream in a meadow or in the forest, you can see large swarms of black flies. In these three to four weeks of the propagation period, it is advisable to avoid these areas completely, because leisure activities are hardly possible due to the infestation. If, on the other hand, only a few black flies get lost in the home garden or on the terrace, then the following can be prevented:

  • spend little outdoors in areas with heavy infestations in warm spring weather
  • the main flight time is about three to four weeks in spring
  • are active at dawn and dusk, as well as during the day
  • not active on days with low temperatures or strong winds
  • even on rainy days, black flies are usually not to be seen
  • Black flies do not stay in closed rooms
  • therefore the greatest security is given here
  • Take warnings from the German weather service about black fly plagues seriously
  • wear long clothing when outdoors
  • pay attention to closable cuffs, closed shoes and hat
  • unlike mosquitoes, black flies cannot bite through clothing
  • do not leave uncovered areas such as the scalp, ears or face unprotected
  • Prevent on all uncovered areas of the skin with mosquito repellents
  • Protect children in strollers with mosquito nets
  • Leave grazing animals indoors during periods of severe infestation
  • light anti-mosquito candles on the terrace
  • a balcony can also be protected with a mosquito net
Note: Like black flies, black flies are also not recognized when they come close to people individually, as they are completely silent and the bite is not noticed at first. Therefore, preventive measures are always very important in areas where the mosquitoes are present.


Black flies are not easy to fight. Insect sprays can be used for short-term protection, for example on the balcony or terrace. However, these do not help if a whole swarm of black flies is approaching. Mosquito repellents that contain DEET offer very effective protection for humans. You should pay special attention to this when buying. Agents containing around 30% DEET offer protection for four to five hours. After that they should be renewed. Coconut oil with a high proportion of lauric acid also helps preventively. It is important that every free skin area is rubbed with the mosquito repellent. Anyone who forgets one or the other free spot, such as the back of a hand or an ear, can be caught and bitten by the black fly despite the remedy.

Tip: If you live in an area where the blackfly infestation is very high, you should consider using insecticides on a large scale. As a rule, however, this is more likely to be taken on by the municipalities.

Symptoms after a sting

If a spot on the arm or leg is itchy or even painful and a small, bloodshot spot can be seen, then it can be assumed that a black fly bite to get at the human blood. After a while, a small knot the size of a lentil can form at the bite site, around which a small purulent blister develops. There is also a one to two centimeter round reddening of the skin around the bite site. Since black flies do not bite like mosquitoes, but rather scratch the skin with saw-like mouthparts, the saliva that gets into the wound can lead to an allergic reaction or an allergic shock, which can even be life-threatening. But in most cases, the bite of the black fly is harmless.

  • Black fly bites can become infected
  • Bacteria on mosquito bites can cause fever or pain
  • Bruises from the bite will itch for weeks
  • If you have an allergy, the area around the bite site can become very swollen
  • in the case of an allergic shock, the person concerned is no longer able to speak
  • he suffers a circulatory collapse
Note : An allergic reaction to the saliva of a black fly can be recognized by severe swelling, itching and pain around the bite site. For example, if an area of ​​the hand is bitten, the entire hand may swell.


If it is a bite without any symptoms worth mentioning, if only a slight swelling can be seen here, cooling is usually sufficient. An ice pad can be placed on the affected area. The various gels against mosquito bites from the pharmacy, which quickly relieve the itching, have also proven their worth. Because it can be particularly dangerous if, for example, small children scratch the spot. In this way, the bacteria secreted by the insect with the saliva are distributed in the wound and can thus enter the bloodstream. And bacteria that are under the fingernail, for example, can also get into the bite wound. Other treatment options are also useful:

  • treat slight swelling with cortisone cream
  • Use disinfectant
  • as a home remedy, a poultice soaked in vinegar helps against the itching
  • Use coconut oil with lauric acid on a bite wound
  • If bacteria got into the bite, use antibiotics
  • only going to the doctor helps here
  • if the swelling is very large, there may be an allergy
  • this should also be clarified by a doctor
  • Symptoms include joint pain, headaches and diarrhea
  • in rare cases, an allergic shock can occur
  • In such a case call an ambulance immediately
  • place the affected person in the stable lateral position

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