Published online by Cambridge University Press: 19 September 2011
Changes in the physiological status of the host rice plant had a profound effect on wing morphism in the brown planthopper, Nilaparvata lugens (Stål). Significant increases in macroptery in the hopper progenies reared on senescent or hopperburned hosts occurred mainly because of a general decline in the host's nutritional status and allelochemic factors. Starvation of young nymphs on nutritionally-depleted hosts probably inhibits the secretion of juvenile hormone by the corpus allatum, suppressing brachyptery and expressing macroptery. Also, any juvenilizing effect of the host's allelochemics would tend to dissipate with the host's senescence. Therefore, the proportion of macroptery in the hopper progeny developing on the rice host plant is determined by the extent of depletion of the host's nutritional allelochemic factors. The observed significant increase in macroptery at a density of 50 or more hoppers per plant may have also been mediated through the host plant. Brown planthopper progenies of macropterous and brachypterous Biotypes 1, 2, 3 and the field population differed in their expression of macroptery probably because of their inherent differences in sensitivity to macropteryinducing stresses.