The Relation of Adult Wing-Form in the Brown Planthopper, Nilaparvata lugens STÅL (Homoptera : Delphacidae) to Wing-Pad Length of Last Instar Nymphs

Abstract

Relationships between adult wing-form and wing-pad length in Nilaparvata lugens were examined under laboratory conditions (25±1°C). Most of the last instar female nymphs with wing-pads shorter than 0.94 mm developed to brachypterous adults, but female nymphs with wing-pads longer than 0.94 mm became both brachypterous and macropterous adults. Thus the brachypterous females of this insect consisted of short wing-pad brachypters and long wing-pad brachypters. In females, with the increase of rearing density during the nymphal stage, short wing-pad brachypters decreased with the increase of long wing-pad brachypters. This was followed by an increase of macropters. Male nymphs with shorter wing-pads tended to become brachypterous adults, but a critical wing-pad size for induction of macropters was not detected. Male nymphs emerged as macropterous adults over the wide density range studied. Relationships between weight and wing-pad length of last instar nymphs were different between sexes. Body weight tended to be heavier in female nymphs with short wing-pads than in those with long wing-pads. The wing morph determination mechanism in N. lugens females was hypothesized to consist of 2 sequential processes. The first process may affect development of wing-pads, while the second process influences development of adult wings.