Development of an assay for the screening of compounds against larvae of the cat flea (Siphonaptera : Pulicidae)

Larvae of the cat flea, Ctenocephalides felis (Bouche), are the target of n umerous growth regulators. This study explores the development of an assay that tests the susceptibility of cat flea larvae to a wide range of compoun ds. Different rearing media and containment units were tested that would fa cilitate optimization. Larvae of various ages were compared, and 7-d-old la rvae were found to be optimal because they were the most uniform in size an d age and exhibited a need to feed. The assay could be used to distinguish insecticides from growth inhibitors. The insecticides chlorpyrifos and carb aryl caused 100% larval mortality in 24 h at 10 ppm, and cythioate and fipr onil killed the larvae at concentrations of greater than or equal to 100 pp m within 24 h. The insect growth regulators methoprene and pyriproxifen cau sed molt delay at concentrations of 100 ppm and bioallethrin delayed molt a t 1,000 ppm. This essay can be used to identify compounds that are specific to cat nea larvae that may be useful in the control of cat flea infestatio ns.