Midges and Chironomids

  • Chironomids are mosquito like insects that vary in size depending on the type of species
  • the adult stage lasts for only a week during which time they swarm as part of the mating process
  • Chironomids occur naturally near all areas of open water
  • Chironomids and their aquatic larvae live in the mud at the bottom of water and are an important part of the food chain for other insects and birds including ducks
  • there are many different species that emerge at different times of the year, from March to October

Are Chironomids a hazard to health?

  • although the swarming of these insects, sometimes in considerable density, can be a nuisance, they are NOT hazardous to health
  • they have no mouth parts and are unable to bite
  • they do not spread disease

Can anything be done to eradicate them?

  • because Chironomids and their larvae are an important part of the food chain for other insects and birds, and because it is illegal to apply any insecticide where there is a risk it could drift into other properties, Thames Water are no longer able to spray the reservoirs with insecticides
  • some reservoirs (including the Staines reservoirs) are sites of special scientific interest (SSSI's), which mean they are legally protected sites of National wildlife importance. Others (again including the Staines reservoirs), are Special Protection Areas (SPA's), legally protected sites of European importance for their bird life. This means that Thames Water have a statutory duty not to adversely affect the wildlife interest of the reservoirs

Because of the restrictions mentioned above, Thames Water are currently investigating environmentally friendly methods to help alleviate the nuisance, these measures include;

  • using water sprays to discourage Chironomids from entering sensitive areas
  • setting up brightly coloured markers in strategic locations which is hoped will attract the Chironomids away from sensitive zones, such as residential areas

What if I need more information?

You can phone the 24 hour Thames Water Customer Centre 0800 316 9800 on or visit their website at https://corporate.thameswater.co.uk/about-us