Presently, mosquitoes are laying their eggs in salt marshes, backyard puddles, abandoned water-filled buckets and anywhere else where they find stagnant water, according to Xu Yuan, director with the Office of the Patriotic Health Campaign Committee in Shanghai.

In a matter of weeks, these insects will mature and start biting humans and animals. Mosquitoes are of particular concern this year in the city as evidence indicates an abundance of the insects this summer. "This year, we set up more mosquito inspection stations, only to discover that the number increased by 70 percent from last year," said Xu Yuan. "That's why we are now staging a mosquito-killing campaign in Shanghai."

When humans or animals breath out, they produce carbon dioxide, and their bodies are constantly giving off heat and moisture. Mosquitoes and other biting insects have the ability to detect carbon dioxide, heat and moisture from long distances and are immediately attracted to the source. Mosquitoes are also attracted to trace amounts of alcohol vapour as well as dark colours, especially black. Mosquitoes fly around and in search of a warm body to bite.

Actually, these insects do not "bite" their victims, they "feed" on them. Female mosquitoes require protein to produce eggs and obtain this protein from the blood of humans and other animals, therefore only female mosquitoes "bite".

A mosquito's lifecycle has four stages -- egg, larva, pupa, and adult. Mosquitoes need water to breed since all mosquitoes spend their larval and pupal stages in water. Therefore, mosquitoes can always be found around water. This is why it is important to clear away stagnant water, standing around your home and apply a larvicide to areas where stagnant water cannot be removed.

The mosquitoes that bite you usually breed within 2 kilometers (1.25 miles) of where you live.

Individuals and communities can reduce mosquito breeding by the following activities:

1. Use sand to fill in pools, ponds, borrow-pits, and hoof-prints in and around homes.

2. Remove discarded containers that might collect water.

3. Cover cisterns (water tanks) with mosquito nets or lids.

4. Clear away vegetation and other matter from the banks of streams -- this will speed up the flow of water.

Pools of water may be caused by leaking taps, spillage of water around stand-pipes and wells, or poor drains. These pools can be eliminated by repairs or improvements to the water supply or drainage system.

Elimination of mosquito breeding in large expanses of water (or in areas where small pools of water are abundant after the rains) usually requires major engineering work.

( June 28, 2002)