Not all mozzies are menacing

2010-02-25 00:00

JUST the very word mozzie causes people to run for the can of insect spray or insect- repelling candles. Let’s chat about these remarkable flies. Most people don’t actually think of mosquitoes as flies, but of course they are, as they possess a single pair of wings and so belong to the important order of insects called the Diptera — or True Flies. Mosquitoes belong to the family Culicidae, and as far as the size of the African fauna is concerned, there are — wait for it — well over 600 species.

Most people know the life cycle and so I will describe it only briefly. Almost all mozzies are blood-sucking, but it is only the females that take a blood meal as they need the protein in order to manufacture their eggs. Males feed on nectar and plant juices and have bushy feelers that detect the whine of females in flight. Their eggs are usually laid in floating rafts and deposited on the surface of still or running water. The larvae and pupae are totally aquatic, but instead of gills they have snorkel-like siphons that break the water surface so that the insects can breathe air directly. Adults usually live within flying distance of their breeding site.

We all know that some of our most dreaded diseases are carried from one victim to another by mosquitoes. Some of these diseases include yellow fever, elephantiasis, dengue fever, encephalitis and, of course, malaria­. What most people do not know, however, is that only a handful of species are implicated in disease transmission in humans­. All the other blood-sucking species feed on animals, never being attracted to humans­. This means that control measures that do not specifically target those mozzies that feed on people can have rather devastating repercussions on other species. One of the ways to control mosquitoes is to cover water with a thin film of oil, thus suffocating the immature stages that are unable to breath through the oil. A consequence of such a blanket treatment is that the species that cause no grief to humans are also killed. Believe it or not, there are deep concerns within the entomological community regarding the wholesale destruction of mosquitoes­. Not only are some species likely to be eliminated altogether, but the effect on ecological processes can be enormous — after­ all, many aquatic animals feed on mosquitoes and so rely on them for their continued existence.

Another interesting fact is that there are the so-called elephant mosquitoes, so named because of their large size. These beasts have a very different biology to most other species. The adults do not suck blood at all, but feed exclusively on nectar, and are probably useful pollinators. It’s the larvae of these mozzies that obtain protein meals as they are predators, feeding on the larvae of other mosquitoes. I was fortunate to get a photo­ of an elephant mosquito as it approached and sucked up nectar from a daisy.

Our problematic, disease-transmitting species usually belong to the genus Anopheles­, and although these occur all over South Africa, we really do not have to be concerned­ unless we live in a malaria area. The fact that mozzies can cause itchy and unsightly spots at the site of their bites is probably the main reason why people detest them and swat them on sight. I am fairly tolerant of mozzies; especially the common black-and-white bush mosquito (Aedes aegyptii) found in virtually every home in KwaZulu-Natal and featured in my other photo. However, I do confess that a mozzie buzzing around my head as I try to get some sleep does bring out the worst in me.

Someone once told me the best way to get such mozzies is this. When in bed and a mozzie flies around your head, merely kick your feet upwards while at the same instance lifting the blanket. The mozzie is sucked into the bed, and all you need do is to roll around a bit to squash it.

• Jason Londt will be at Flavour Café, Dunrobin Nursery, between 9 am and 11 am on March 13 should anyone wish to chat to him or purchase a copy of his recently published collection of Witness articles.

• Dr Jason Londt is a natural scientist with a special interest in entomology. He welcomes queries and comments, which can be sent to him at jasonlondt@telkomsa.net

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