A Wrong Mosquito Trap?

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It is the mosquitoes’ summer party time! The swarming mosquitoes are not only a nuisance that cause itching, but are dangerous vectors of viral diseases such as Japanese encephalitis and Dengue fever. So every measure is taken to exterminate the little creatures. In many parks, housing estates and schools, we can see sticky yellow paper traps set up in the outdoor space. While you may think that we have succeeded in our mission, you may be disappointed to find that the paper traps that are all covered with bug corpses are actually an illusion – they may even cause the mosquito population to boom!

The yellow paper traps lure insects that are attracted to the colour. However, mosquitoes and biting midges follow mostly the body temperature and carbon dioxide as they feed on animal blood. These little bugs will not fall onto the yellow traps. Indeed, what usually caught on the paper traps are innocent insects that feed on nectar or plant sap. The trap is not the proper tool to tackle the mosquito problem.

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On the other hand, the sticky paper traps full of bugs are inviting to insect-feeding animals. Unfortunately, they are also doorways to death in some cases. As the predators approach the feast, they are easily glued and hurt, and may even starve to death. Geckoes’ bodies, or torn feathers of birds, are often found on the paper traps. People have also shared on social media how they have saved birds stuck on the traps and cleaned the glue from their feathers—however, not all of them survive. It is ironic that the traps set up to kill mosquitoes turn out to harm geckoes and birds that prey on mosquitoes. When the natural enemies are reduced, mosquitoes thrive.

In view of this, in 2019 the Hong Kong Wild Bird Conservation Concern Group collected photographs on social media and expressed concern to the Leisure and Cultural Services Department. The department has since stopped the use of sticky paper traps in all leisure venues under its management. However, the measure has not been followed by private housing estates, schools and public housing estates under government’s management. Today we are still seeing the widespread use of sticky paper traps in open space.

To tackle the problem of mosquitoes and biting midges, the most effective ways are to remove any still water that the creatures rely on for breeding, and clear debris and refuse in public open spaces such as flower beds to keep the soil dry. With good ventilation and a dry environment, mosquitoes and biting midges can be properly controlled. Mosquito killing machines can also be installed if necessary, which cause less harm to other innocent animals.