Increased Cases of Black Fly Bites

Spain raises alarm over black fly which can spread viruses

Spain raises alarm over black fly which can spread viruses Source: Wikipedia

ANECPLA, the National Association of Environmental Health, have urged the government to take measures to control the spread of the black fly plague this summer. The black fly is known for its aggressive bites, and more people are reporting bites at health centres across Spain.

What is the Black Fly?

This endemic Spanish species has been spreading exponentially in recent years, and the fly’s bites can be painful and cause infection or allergic reactions, even resulting in hospitalisation in some cases.

These insects are active during the day and can cover long distances, populations increase between the months of May and October. This year, the lack of rainfall and decreased river levels has been favourable for increasing the fly population.

The fly feeds on blood by puncturing the skin with its saw-like jaws to extract blood, depositing a small dose of an anaesthetic, so the unwitting victim is unaware of the bite for up to five minutes. The bites often swell into a welt that can be up to a few centimetres long that can last up to a month, it is also common for the bites to bleed.

The flies do not transmit any diseases.

What To Do if You’ve Been Bitten

If you have been bitten by this insect, you should apply ice to reduce the swelling. Mild corticosteroid cream can be applied to reduce inflammation. Scratching should be avoided, which may exacerbate the wound.  Allergic reactions usually manifest as a fever or reactions on the skin that are more intense and painful than usual, but serious complications are rare.

Affected Regions in Spain

Black flies have been reported in high numbers in Andalusia, Aragon, Catalonia, Madrid, Murcia and Valencia. Regions near the Ebro river are most affected by these insects, as they need bodies of water to reproduce. ANECPLA emphasises the importance of controlling fly populations with regular cleaning of rivers and bodies of water.

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Written by

Lisa Zeffertt

Lisa is British, born in Hong Kong and has lived in many countries including the UK, Hong Kong, Cyprus, and Thailand, Spain has been her home for the past 10 years. After graduating with a BA in English Literature and Art History, she has worked in different sectors, most recently as a ghostwriter and translator for six years Writing is one of her passions, as well as working in both Spanish (fluent) and English.


    • Martin

      03 August 2023 • 11:04

      I have been bitten many times in the countryside of La Nucia for the last 2 years. Nasty bites that swell and last between 2 – 6 days. What are they called apart from a black fly?

      • John Smith

        03 August 2023 • 11:58

        Martin, in Spanish they are simply Mosca Negro and there doesn’t appear to be any other common name for them. If it’s any help for research, the Latin name is Simulium erythrocephalum.

        • Martin

          04 August 2023 • 20:09

          Thanks, John. I looked it up. They are out and about around dusk and dawn.
          Simulium erythrocephalum (De Geer, 1776) is a highly anthropophilic species responsible for black fly outbreaks in Spain. Thus, observations were made on the mating behavior of S. erythrocephalumunder natural conditions in Spain, including swarm formation, recognition, approach and completion of copulation and post copulation behaviour. The results obtained showed that copulation activity takes place during the afternoon. We observe how the human being represents an attractive orientation marker for the swarms of males, whose formation is related to the period of host search activity by the females. This study represents the first study on the mating behavior of blackflies in Spain, expanding the general knowledge about this behavior in blackflies.

          • John Smith

            05 August 2023 • 12:27

            Thanks Martin – visiting the EWN website certainly helps to improve ones knowledge

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