Formamidine penetration of cuticular preparations from diapausing and non-diapausing southwestern corn borer larvae
1983
GAYEN, APURBA K. | McKEE, MICHAEL J. | Knowles, Charles O.
Penetration of six formamidines into and through the isolated abdominal cuticles of nondiapausing (NDL), environmentally induced diapausing (EIL), and hormonally induced diapausing (HIL) southwestern corn borer larvae was assessed by means of a two compartment model which consisted of the outer compartment comprised of the external radiocarbon and the inner compartment comprised of the radiocarbon in the cuticle and in the hemolymph. Penetration was non-linear and was due to the decrease in rate of movement of formamidine from the outer to the inner compartment as equilibrium between the compounds in the two compartments was approached. There were differences in penetration rates among formamidines and larval types. Scanning electron micrographs revealed that cuticles of EIL and HIL but not NDL contained heavy deposits of wax. It was suggested that this epicuticular wax played a role both in facilitating formamidine penetration and in delaying formamidine release from the cuticle into the hemolymph in some cases. This study has demonstrated that cuticles of non-diapausing and diapausing southwestern corn borer larvae responded differently to formamidine probes. Such differences were likely a consequence of juvenile hormone mediated changes in the physiology of the cuticle and may have practical significance from the standpoint of chemical control of this pest.
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