Susceptibility to insect growth regulators and cuticle deposition of the cat flea (Siphonaptera : Pulicidae) as a function of age

Wandering larval, pharate pupal, pupal, and pharate adult stages of the cat nea, Ctenocephalides felis (Bouche), were identified bl: examination of cu ticular cross sections via scanning electron microscopy. Visible morphologi cal characteristics of each stage were identified and described. Various st ages of the nea throughout metamorphosis were exposed to juvenile hormone m imics and insect developmental inhibitors. Wandering lan ae treated with ju venile hormone mimics were unable to pupate, whereas treated pharate pupae ecdysed to the pupal stage but were unable to eclose. Pupae and pharate adu lts did not succumb to juvenile hormone mimic exposure, even at concentrati ons 3 orders of magnitude magnitude greater than those that killed 100% of the wandering lan ae and the pharate pupae. Adult females were more suscept ible to juvenile hormone mimics than males. Possible explanations for the v ariation in tolerance to juvenile hormone mimics of the differing stadia ar e discussed. None of the stages were susceptible to insect developmental in hibitor exposure. Analysis of catecholamines that are precursors of cuticle sclerotization and melanization were measured in the wandering larval thro ugh the pharate adult stages of the cat nea. N-acetyldopamine concentration was highest in the pupa stage when the flea had a hard clear cuticle; N-be ta-alanyldopamine concentration was highest during the production of the ha rd, dark cuticle of the pharate adult and dopamine fluctuated throughout de velopment but was highest in the pupal stage.