Friends of Rietvlei
Member of the Wildlife & Environment Society of South Africa Western Cape Region
Eco Bites
Midges or Muggies
It is that time of the year again – with the warmer weather the little flying terrors are out in force.
Midges, 'muggies', gnats – call them what you like, they are a nuisance and many residents in are being severely pestered by these little guys.
What are they, and where do they come from?
Midges, gnats or muggies is a name applied to a wide range of small flies. These are members of the order Diptera (meaning two-winged: di = two, ptera = wings), this is the order to which all flies belong. Midges are not a well-defined group, but are spread throughout at least ten families in the suborder Nematocera. This means that their life-styles and biology differ considerably; some feed on nectar or decomposing plant material, a few feed on blood, and in some species the adults do not feed at all.
Female gall midge laying eggsLike all Diptera they have four life stages: egg, larva, pupa and adult. The larval stage in most midges, with the exception of the gall midges, are aquatic. This means that the eggs are laid in or near water or very moist areas, the larvae are found in the water, in mud in the bottom of rivers, lakes or ponds, or even in very wet leaf mould in forests and other damp places. Some larvae will inhabit wet animal dung. The larval stage for midges vary from only a few days long, to several years in cold climates; they larvae feed on detritus, diatoms and other microscopic plants and animals.
The larvae turn into pupae, this is mostly a fairly short stage, mostly only two to four days, although there are exceptions where the pupal stage is longer. The pupae do not feed at all.
Gall on plantThe adults will hatch from the pupae, and these are the little fellows that are such a nuisance to us. Most species are completely harmless, but there are some that can cause problems. The gall midges in the family Cecidomyiidae are important plant pests which can affect crops. The biting midges in the family Ceratopogonidae are serious pests and are responsible for spreading livestock diseases like Blue Tongue in cattle and sheep and African Horse Sickness.
The female biting midges must have a blood meal for their eggs to mature, while feeding they transmit parasites – most of these parasites affect livestock and game, but the midges can infect humans with filarial worms of the genus Mansonella. This infection is not serious as the worms are only located in the skin, but it does cause dermatitis and skin lesions.
The most common midge or muggie that pesters us here in our area are non-biting midges of the family Chironomidae. There are over 5,000 species occurring all over the world, from the Arctic regions in the north to the Antarctic in the south, the adults are small and resemble mosquitoes – but most of them do not feed at all.
Chironmid 'bloodworm' larvaA distinguishing characteristic of several chironomid species is that the larvae have haemoglobin in their blood, this means that their blood is red – these are often known as bloodworms. They can store oxygen in their blood which allows them to survive in deep water or in water where the oxygen content is low. Many of the local species of chironomid have bloodworm larvae, you can find these larvae quite commonly in ponds and small water bodies in the area.
Adult chironmidWhile adult chironomids are harmless, they can be pests when they emerge in large numbers. They can damage paint, brick and other surfaces with their droppings, and when they die they build up in piles. Sometimes these piles of dead muggies provoke allergic reactions in sensitive individuals. In most areas chironomids breed once or twice a year, but if conditions are good they can breed up to four times. Each breeding cycle delivers a swarm, so we can have swarms up to four times a year; another factor is that breeding in different water areas are staggered, so one could be suffering a series of swarms from different water bodies, or even from the same water, for a few months at a time.
While they are a nuisance to us, chironomid larvae and pupae are important as food for fish, amphibians and other aquatic organisms; the adults are a very popular food source for insectivorous birds such as swallows and martins. Chironomid larvae are also useful as an indicator of water quality – the presence or absence of various species is an indication of the quality of the water. Some like the bloodworms become more numerous in polluted waters where oxygen levels are very low, other members of the family are intolerant of poor water quality and will only be found where the water quality is good.
How do you deal with these pests?
In the daytime they are a nuisance if you happen to walk into a swarm; the real problem is at night as they are attracted to lights. If they really are a continuous nuisance, the only way to keep them out of your house is to put up mosquito netting. There are insect repellents on the market today that will help, most of these insecticides are specific to insects and will not affect humans or pets in the house; the evaporative repellents (those that are plugged into a wall plug) for mosquitoes are quite effective to keep a room clear of midges.
And what about mosquitoes?
Midges are sometimes confused with mosquitoes, but mosquitoes are in the family Culicidae – read more about them ....  Click here
Click here to read more about aquatic insects.
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