Black flies are thriving in Spain’s heat: how to avoid their bites

Black flies are thriving in Spain's heat: how to avoid their bites
Year after year, ANECPLA has increased the alert level for the prevalence of la mosca negra (black fly) in urban areas across Spain. Photo: Wikipedia
Spanish pest control companies are warning of the sharp increase of black flies caused by the very high temperatures recorded across the country. Here are the expert recommendations for avoiding their blood-sucking bites.

What’s the latest?

If it strikes you that during the summer there’s a spike in the number of warnings about all the creepy crawlies that are biting and stinging holidaymakers, you’d be right. 

In recent weeks health experts in Spain have been warning residents and visitors about the proliferation of ticks in several regions across the country, and a British tourist recently had to have two fingers amputated after being bitten by a recluse spider in Ibiza.

Now Spain’s National Association of Environmental Health Companies (ANECPLA) is alerting the population that the episodes of extreme heat being recorded across the country are resulting in a huge increase in the number of black flies, referred to as mosca negra in Spanish. 

“The black fly bite is in the shape of a saw that leaves a bleeding and extremely painful cut that can become infected,” Spain’s National Association of Environmental Health Companies (ANECPLA) warns.

“High temperatures are one of the main factors leading to a peak in the volume of the black fly population,” ANECPLA’s CEO Jorge Galván added.

In other words, the intense heat of Spain’s latest heatwave has meant that more larvae are surviving in riverside vegetation.

“Their lifespan, which can last from a few days to several months, can be reduced by half when it is very hot, as what’s happened during Spain’s latest heatwave, thus producing a demographic ‘boom’ and consequently an increase in bites.” 

Just like with other insect species, scientific studies show that climate change encourages their reproductive cycle, particularly in areas close to rivers where they tend to live. 

Increased conservation and maintenance of rivers in urban areas has also helped them thrive, as black flies proliferate in clean and circulating bodies of water.


Where are they proliferating in Spain?

In 2021, Aragón, Catalonia, the Valencia Region and Madrid are the regions which have seen the biggest increase in their black fly populations. 

A drop in bat populations has also meant they have no natural predators to keep numbers down. For over a decade, authorities in Zaragoza have been trying to increase the bat population around the Ribera de Ebro protected area to address the problem.

Residents of the district of Villaverde outside of the Spanish capital have been plagued by black flies this summer, attracted by the abundance of vegetation, the nearby Manzanares river and the swimming pools.

“We have to go outside in long sleeves because they bite you, even if you use mosquito repellent,” one resident told local TV channel Telemadrid, insisting that it’s preventing outdoor activities from taking place in Villaverde.

Year after year, ANECPLA has increased the alert level for the prevalence of la mosca negra (black fly) in urban areas across Spain.

What to do if you get bitten by a black fly and how do you avoid it?

Black flies – also referred to as buffalo gnat, turkey gnat, or white socks – don’t sting, they bite. 

This 6mm insect is in fact looking to suck blood just like a mosquito, but as the amount they ingest is usually greater, the pain is more intense and long lasting. 

You may not feel the bite initially as the black fly injects an anesthetic that is both a vasodilator and an anticoagulant, allowing them to go unnoticed while feeding.

The bites are not venomous but they can cause swelling or bleeding and in some cases an allergic reaction, in which case it’s advisable to go to the emergency room.

Other symptoms can include headache, nausea, fever, and swollen lymph nodes.

If you do get bitten, try to avoid scratching the wound, wash it and disinfect it. You can apply ice or a recommended scream. 

Pay special attention if you’re in a part of Spain that’s close to a river, although black flies are found all across the Spanish territory. 

Unlike other flying insects, the black fly acts during the day (particularly active in the early morning and in the evening) and is able to get under clothing and reach the skin to achieve its goal.

Some of the tips released from ANECPLA to avoid being bitten by this insect are as follows:

  • Dress in light clothing and avoid bright colours that can attract swarms.
  • Avoid walking along the riverside or in closeby areas, especially in the late afternoon.
  • Install mosquito nets on doors and windows in risk areas.
  • Avoid the accumulation of water outside of your home.
  • Keep swimming pools, water tanks and other water deposits covered when not used.
  • Check your home’s drains and sewage system.
  • Use certified repellants (especially those containing citronella).
  • Contact professionals if you’ve been unable to solve the issue.

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