Effect Of Temperature On Reproduction Behavior In Brachypterous Females Of The Brown Planthopper, Nilaparvata Lugens

The brown planthopper (BPH) Nilaparvata lugen (Stal) (Homoptera:Delphacidae) is an important migratory pest in rice, widely distributed in the Yangtze River Valley and the south and southwest rice planting areas of China. Brachypterous adults of the BPH are more sensitive to environmental factors, and cause greater loss of production than macropterous adults of the BPH. In order to understand the effect of temperature on reproduction in brachypterous adluts of the BPH, the present thesis investigated: (1) effect of temperature on mate-finding and mating behavior; (2) effect of delayed mating on reproduction. The results of the current study may shed light on population forecast of BPH.Effect of temperature on mate-finding and mating in brachypterous females of the BPH were investigated under three temperatures 20℃,28℃and 32℃. Results showed that rates of mate-finding by males were significant higher at 28℃than at 20℃or 32℃at different time intervals (30 min,60 min,90 min,120 min,150 min and 180 min) since the initiation of the observation. After 200 min, the rate of mated females in BPH was also significant higher at 28℃than at 20℃or 32℃. The rates of vibrating females at 20℃and 32℃were significantly lower than that at 28℃, decreasing by 28% and 72%, respectively. The total vibrating duration at 28℃was 2.41 and 43.0 times higher than those at 20℃and 32℃, respectively. Males did not vibrate at 32℃, the vibrating rate at 20℃was reduced by 40% compared to that at 28℃, and the total vibrating duration at 28℃was 52.7 times higher than that at 20℃. Compared with those at 28℃, the vibrating frequency were significantly lower at 20℃and 32℃in the females, but no differences between temperature treatments were detected in vibrating duration in the females and, vibrating frequency and vibrating duration in the males. The rate of males responding to female vibration was significant higher at 28℃than those at 20℃and 32℃. The mate-finding duration in males was significant shorter at 28℃than those at 20℃and 32℃.Effects of delayed mating on reproduction were investigated for brachypterous females of the brown planthopper, N. lugens. Five different treatments, including mated females at 2,4,6,8 and 10 d, were designed. Females, mated at 4,6,8, and 10 d after emergence, showed decreasing fecundity with the increasing age; females mated at 4 d after emergence oviposited the most eggs (about 337 eggs) and females mated at 10 d after emergence oviposited the lowest eggs (about 168 eggs). There were no significant differences in cumulative egg-laying rates between females mated at different ages.