Altosid Pellets WSP contains Altosid, which is an insect growth regulator to prevent adult emergence of water mosquitoes or floodwater mosquitoes. This will help with preventing the spread of West Nile Virus, which can be found in adult mosquitoes. This product will continue to release for up to 30 days. Treated larvae will continue to grow at a normal rate to the adult stage (pupal stage) where they die. This insect growth regulator will not work on mosquitoes which have reached the pupal or adult stage before treatment. Each bag comes with 50 ready-to-use, water soluble pouches. Each pouch will cover up to 135 sq feet of water surface area. They are water sensitive and when it touches water, the pouches will dissolve and release the pellets. Easy to use, these are ideal for treating water sites that are hard to reach like roadside ditches, storm drains, catch basins, and other artificial or natural water-holding containers.