Abstract
The insecticide diflubenzuron (DFB), a benzoylphenyl urea, decreases fecundity in insects by a still unknown mechanism. The objective of this study was firstly to see the effects of DFB on female reproduction, after its ingestion by Schistocerca gregaria females five days following imaginal molt. DFB significantly delayed the timing of the first and of the second laying when compared to control females. DFB-treated females laid eggs only twice, while control females had, as typical, up to five ovipositions. DFB action on ovarian development and hemolymphatic ecdysteroid levels were also evaluated in females. Ecdysteroid titres in control females fluctuated according to the ovarian cycle, reaching a peak of around 170 pmol/mL hemolymph during the vitellogenic phase. In DFB-treated females, hemolymph ecdysteroid titres remained very low and oocyte growth was reduced. The treatment caused early oocyte resorption and any eggs deposited never hatched.
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