Altosid Pellets WSP Mosquito Growth Regulator release (S)-Methoprene, an Insect Growth Regulator as they erode. ALTOSID Pellets WSP prevent the emergence of adult standing water mosquitoes, including Anopheles, Culex, Culiseta, Coquillettidia, and Mansonia spp., as well as adults of the floodwater mosquitoes, such as Aedes, Ochlerotatus, and Psorophora spp. from treated sites.Active Ingredients: (S)-Methoprene 4.25%Insecticide Mode of Action Group: 7 Insecticide Class: Insect Growth RegulatorEPA Signal Word: CAUTION / PRECAUCIONApplication Rate Range: (see label) Container Size(s): 50 x .7g