Modirisk: the biodiversity of mosquitoes

You're lying in bed and just as you're about to doze off you hear an irritating whining in your ear: a mosquito has come to disturb your good night's sleep. Insect expert Wouter Dekoninck knows the culprit: “it’s probably the house mosquito, Culex pipiens. That's by far the most common mosquito species in Belgium and it's responsible for almost all mosquito bites on people.”

There are a lot of other mosquito species in Belgium, but despite this, until recently very little was known about the biodiversity of Belgian mosquitoes.

“There's been no organised scientific research programme on this since the 1940s”, says Wouter. “Two years ago we started again from scratch with project Modirisk, which aims to chart mosquitoes in Belgium.” The scientists of Modirisk wanted to know about native species, but what interested them most is whether there are also exotic species to be found in Belgium. Increased international movement of goods and people has made it easier for exotic species to spread. Global warming also adds to the risk that tropical flies could establish themselves here. That could have important consequences, because those exotic species can bring diseases, such as malaria, with them.

To catch the mosquitoes, the scientists used special traps that work using propane gas, which is converted into water, CO₂, and heat. “Mosquitoes locate their prey using body temperature and exhaled CO₂, so they are irresistibly attracted to the traps”, explains Wouter. “A third way in which they find their prey is through smell. In people, body odour is different for every individual, which explains why some people get bitten a lot while others hardly ever do. However, only the females actually suck blood – they need the protein to lay eggs. The male mosquitoes live on a strictly vegetarian diet of nectar and other plant juices.”

“After three years of intensive trapping in more than nine hundred different locations, in cities, agricultural, and natural areas, we now know that in Belgium there are a total of 30 different species of mosquito,” says Wouter. “Some species only suck blood from frogs and toads. Most are less choosy and also bite birds, rodents, or people and other large mammals. It was obvious that certain species are found only in forests, while other species spend their winters in houses and thus live mostly in urban areas. We were also able to determine that there are currently two exotic species that live in Belgium, both of which come from Asia. They do feed on human blood, but they aren't very aggressive. They are, however, potential carriers of viruses that in some cases could cause a deadly form of meningitis. Luckily, these viruses are not seen in Belgium, for the time being, so there is no reason to panic. Thanks to Modirisk we will shortly be able to evaluate the risks of outbreaks of other, similar diseases. If necessary, we can let the authorities know, and thus take the appropriate pest control measures.”