Killing Mosquitoes by Luring Them to Lay Eggs

The University's luxuriant campus is something to be proud of yet lush greenery also provides optimal breeding grounds for mosquitoes.

Mosquitoes are not only a nuisance; they are the prime culprits for spreading diseases such as Dengue fever and malaria. To protect the health of campus members, the University is committed to combating these potentially lethal creatures.

Beginning in mid-2005, ovitraps have been placed throughout the campus to identify mosquito breeding black spots for the sake of fighting mosquitoes more strategically.

The University Safety and Environment Office is responsible for placing ovitraps and processing the data received. Mr. Lam Shi-kai, safety manager of the office, said, 'We place ovitraps at 15 different locations on campus, for seven days at a stretch. We then tally the number of pupae and change locations monthly.'

The ovitraps are provided by the Department of Food and Environmental Hygiene. They are black cylinders of 200 ml each and come with a brown paddle. The paddle is dipped in water to lure female mosquitoes to lay eggs. Mosquito pupae usually take nine days to develop so the ovitraps are retrieved after seven days.

Mr. Lam said, 'Ovitraps are placed at black spots where Aedes pupae or pupae of other mosquitoes have been found. We will continue to place ovitraps to monitor the situation; at the same time, we will notify staff of the Estates Management Office to keep grass short and trimmed, clear away stagnant water and spray insecticide.' He added that it is hard to distinguish between Aedes and other mosquitoes. His office has sent a staff member who is on loan from the Department of Microbiology to undergo training at the Department of Food and Environmental Hygiene to learn how to differentiate Aedes from regular mosquitoes. 'Aedes mosquitoes are characterized by white stripes on their bodies but these are barely visible to the naked eye. Ovitraps also attract other insects to lay eggs. Therefore we have to magnify the larvae under a stereomicroscope for proper identification.'

Reviewing the data of the past year, Mr. Lam remarked, 'The campus is inhabited by many species of mosquitoes. It is hard to say which predominate but luckily the Culex mosquito which transmits Japanese encephalitis is rarely found. Most pupae were recorded in August and September. These were also the busiest months for EMO staff. During the orientation camp for new students, especially, measures for eliminating mosquitoes were stepped up.'

Mr. Lam calls upon members of the University to notify the EMO by phone at 2609 6666 if they ever stumble upon favourite mosquito haunts or puddles of stagnant water.