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Zeekoevlei’s Midges or ‘Miggies’

10 Oct 2011 Posted by in Environment | 4 comments

What they are and how to minimise their ‘impact’ on you

Spring has arrived, with summer on its way, and with these seasons comes the arrival of swarms of midges (or commonly known as ‘miggies’) in and around Zeekoevlei. Following on from complaints by residents about the ”plagues of miggies” experienced in previous years, and the nuisance impact of these, a study was conducted by an intern at the City of Cape Town, in conjunction with Dr Liz Day of The Freshwater Consulting Group.
Some of the main objectives of the study were to:

  • Describe the extent of the midge problem at Zeekoevlei
  • Highlight its impact on the community
  • Comment on the ecological significance of midge populations in the vlei ecosystem
  • Recommend environmentally sensitive control measures to minimise midge impacts

 

What is a midge?
A midge is the most common wetland invertebrate and belongs to the Class Insecta (insects), Order Diptera (flies). There are 300-400 species in southern Africa, and 10 000-15 000 species worldwide.
The midges one sees flying about are the adult form, and have very short life spans out of the water.

The diagram below shows the life cycle of a midge:

Males form breeding swarms over distinct objects at particular times of the day (species dependant)

Females lay 1 000-2 000 eggs

 

Study approach and results
Sediment samples were taken in both muddy and sandy sites, and these were analysed in terms of the number of larvae per square metre (m2) and the dominant midge type or species.
Sandy sites were dominated by midge larvae of the genus Cladotanytarsus, which are small (2-3 mm) mainly tube-dwelling larva, whilst muddy sites were dominated by midge larvae of the genus Chironomus, which are large (>20 mm) red in colour and adapted to low oxygen conditions.
Very low populations of midges were found in muddy sites ( As water quality in the vlei improves, it is likely that the extent of sandy areas will also increase. Sandy areas are desirable from both a recreational and an ecological perspective, as they represent a decrease in areas of thick, anoxic, foul-smelling muds.)
Although undoubtedly a nuisance to local residents, the midge populations at Zeekoevlei are not approaching ‘plague densities’, which are regarded as 50 000 individuals per m2. Further, literature suggests that the peak populations that occur in spring in the Zeekoevlei area are a natural phenomenon even in unimpacted wetlands.
Management options
It is clear that whilst natural predation of the insects by, for example, fish and birds will help control the populations of midges, they will still be prevalent in the area, especially during spring and summer, given their life-cycles and the type of wetland areas they inhabit.
Behavioural control, that is our adaption of behaviour in response to the ‘miggie issue’, is the most effective way of minimising the midges’ nuisance impact on our lives.

What can you do to minimise the impact of ‘miggies’ on your life?
The following are some proposed measures that could reduce the impact the midges have on you, the resident living in proximity to Zeekoevlei:

  • Manage property lighting, by avoiding the use of white light;
  • If possible, avoid hanging your laundry up to dry on calm sunny days in spring/ summer whilst the midge populations are at their greatest;
  • Close doors and windows at night during peak periods of midge activity;
  • Install insect screens on doors and windows;
  • Try to avoid painting buildings/ structures white.

It is important to remember that living close to a wetland such as Zeekoevlei, will result in sharing your space with the natural creatures that survive in such ecosystems. These can both be beautiful, such as the majestic birds, or annoying, such as the midges. Both however are part of an integrated ecosystem, and fundamental to it.
The advantages of living close to such an amazing natural resource as Zeekoevlei need to be considered in offset against some of the ‘natural nuisances’ that can be experienced.
For more information contact Asieff Khan or Joshua Gericke at the False Bay Ecology Park on telephone 021 396 4281.

September 2011

  1. Dee10-10-11

    With a photo like that on an article like this …

    …. I guess they pronounce your name Aah-sif! The “Aah” for the good looks and the “sif” for what we think of midges squashed into the laundry!

    Apologies I reckon I better wear sunglasses after that!!

    Thanks as always for keeping us safe and in love with our beautiful vlei

    xx

  2. Freya10-11-11

    Is it really not “plague level”? Those of us who do water sports (rowing in particular) find it almost unbearable to row with these. They fly into your eyes, nose and mouth and there are (not exaggerating) about a hundred settling on you at a time.

    Another thing that concerns me it that you mention the fish playing an important role in the management of the “miggie” species but I am at a loss to explain how the fish would survive in water as polluted as that of Zeekoevlei’s.

    I am shocked at the levels of it. There is always “something being done” about it but I personally don’t see it happening. I apologise if this is not the case but I think you need to step up your game. The thing that makes me seethe is that this is supposed to be a nature reserve but I see dead fish washing up on the shore along with countless plastic bags and other rubbish.

    One of our boats capsized on the water, the rowers were complaining about burning eyes. I am not sure if this is anything to worry about, but still, what does this say about the state of the water?

  3. James10-13-11

    The City is accountable and the way they have conducted themselves is nothing short of criminal- to allow the situation to deteriorate as it has done. http://www.bottomroadsanctuary.co.za is my website where i have posted the two recent articles that appeared over the last week or so in the cape Argus and other commentaries with regards to the current situation.
    A montha go i asked the City to call an immediate crisis re Zeekoevlei- to this day they just ignore you and continue to make countless excuses- we have buried approx. 20 fish in the Bottom Road Sanctuary.

  4. Steve10-13-19

    This is a plague and getting worse every summer. The Milnerton area is infested as they blow all the way here from quite possibly Zeekooivlei in the South Easter. The last 3 years have been chronic. They need to be controlled at source.

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