Calmodulin is a ubiquitous Ca2+-binding protein, which has numerous functions in cell biology, including cAMP-dependent signal transduction and cell division. Drugs with a phenothiazine ring system have been used for decades in the treatment of schizophrenia and other psychoses,
and their anticancer potential has been reported. Here we present the first evidence for the disruption of normal insect development by low doses of two typical phenothiazines, chlorpromazine and trifluoperazine, administered via a semi-synthetic diet to larvae of the cotton
leaf worm (Spodoptera littoralis; Lepidoptera, Noctuidae), a polyphagous pest of various crops. At 0.3 percent trifluoperazine in the diet the development of the larvae to the adult stage was completely prevented. In view of their moderate toxicity to vertebrates, including
humans, and in view of the availability of numerous phenothiazine drugs at reasonable costs, agricultural applications of phenothiazines appear possible.