Mosquito Magnet Lurex3, a patent-pending mosquito attractant, mimics naturally occurring human skin scents or odors that attract mosquitoes. It has been designed for use with all Mosquito Magnet traps. The EPA-registered Mosquito Magnet Lurex3 is the only attractant proven to attract the Asian Tiger Mosquito. It also attracts other species of mosquitoes that may transmit diseases such as West Nile Virus, Encephalitis, and Heartworm. The Mosquito Magnet Lurex3 cartridge should be replaced every 21 days. After 21 days of use, the cartridge appears the same; however, it will no longer be effective as the Lurex3 will have been released. The catch rate will be reduced if the attractant is not changed. Using a secondary attractant is critical to the performance of your Mosquito Magnet trap. Once mosquitoes sense the carbon dioxide from the Mosquito Magnet, they need a secondary attractants, Octenol or Lurex3, to hone in on the trap. Lurex3 should be used in southern regions of the U.S. and in Hawaii, where the main types of biting insects include the day-biting Asian Tiger Mosquito and other mosquito species as well as no-see-ums and black flies. Those in coastal areas in the Southern regions, however, should use the attractant Octenol. 3-pack.