Effects of a new insect growth regulator, CGA-255 ' 728, on the different stages of the cat flea (Siphonaptera : Pulicidae)

A new juvenile hormone mimic CGA-255'728, developed by Novartis, was tested for its efficacy on different life stages of the cat flea, Ctenocephalides felis (Bouche). The compound was mixed in bovine blood at concentrations o f 1, 10, and 100 ppb and fed to adult fleas using an artificial membrane sy stem. Less than 7% of the eggs from fleas fed 10 and 100 ppb hatched, compa red with >70% hatch in eggs laid by control fleas or fleas fed 1 ppb. Histo logical studies demonstrated that approximate to 50% of the eggs from fleas fed 10 ppb contained unhatched larvae that died after completing embryolog ical development. At 100 ppb, 24% of the fleas died as fully formed larvae within the egg, but at this concentration nearly 20% of fleas also died bef ore embryogenesis was completed. In addition to embryonic and larval mortal ity, approximate to 28% of eggs from the 100 ppb-treated group were deposit ed as empty shells. Evidently these eggs were crushed by the muscular actio n of the oviduct and yolk was expelled into the oviduct during oviposition. None of the test concentrations showed adulticidal effects over a 10-d per iod. Fecundity was significantly increased with increased concentrations of CGA-255'728 indicating that the compound mimicked the effect of juvenile h ormone.