A proposal to build 2,000 flats could be defeated by a 10mm firefly if two environmental groups have their way. The Conservancy Association and the Entomological Society said yesterday that a new firefly species, discovered last year in Hong Kong Wetland Park, lives just 300 metres from the Cheung Kong development site. The groups have urged the developer to halt the residential project at Fung Lok Wai, Yuen Long, and review the environmental impact assessment completed in 2008. The Maipo bent-winged firefly was identified by international experts last year as a species new to science. Members of the Conservancy Association and the Entomological Society said they have seen many of the fireflies in the mangroves and streams east of the wetland park. 'Tin Shui Wai new town is at least 800 metres from where the fireflies were sighted,' said Peter Lee Siu-man, campaign manager of the association. 'I'm concerned the proposed project will be too close for them to bear.' The firefly has a body length of about 8-10mm and a dark brown back. A distinctive feature is the hooked wing covers of the male, which serve as a clamp to hold the female during mating while at the same time keeping other males away. The environmental impact assessment report for the Fung Lok Wai project was written before the species was identified. Half of the 80-hectare Fung Lok Wai site, largely abandoned fish ponds within the Deep Bay Area, is listed in 1995 as a wetland of international importance. Mutual Luck Investment, a Cheung Kong subsidiary, has proposed building 19 blocks of 2,000 flats on 5 per cent of the Fung Lok Wai site. The rest would be preserved under a conservation foundation yet to be set up. A spokeswoman for Cheung Kong (Holdings) said its project would put in resources to conserve and enhance the wetland and would create freshwater marshland habitat. Ecologists will research and monitor the environment and the conservation work will be overseen by an independent committee . WWF (Hong Kong) has signed a memorandum with the developer, agreeing to manage the reserve. All other green groups have objected and have urged the government to swap land with the developer. The development proposal has been posted on the Town Planning Board website for public comment until Friday. The board will vet the project next month.