Diurnal Periodicity of Flight Behaviour of the Brown Planthopper, Nilaparvata Lugens STÅL, in the 4th and 5th Emergence Periods

Abstract

Daily periodicity of flight activity of the brown planthopper, Nilaparvata lugens STÅL, in the 4th and 5th emergence periods from late August to early September and late September to October, and that of the green rice leafhopper, Nephotettix cincticeps UHLER, in the same period was investigated with a JOHNSON& TAYLOR'S suction trap of 12 inches. N. lugens adults took off at sunrise and sunset in late August. Light intensity adequate for take-off was about 1-200 lux. It was considered that the periodicity of N. lugens was a bimodal crepuscular type. But in the later season as a result of suppression by low temperature three types of flight periodicity curves were observed. Namely, bimodal crepuscular, unimodal crepuscular at sunset and diurnal. The threshold temperature for take-off was about 17°C. Flight behaviour was also suppressed by wind of over 11km/hr. N. cincticeps adults took off only after sunset. Light intensity for take-off was 0.1-20 lux, considerably lower than that for N. lugens. Take-off was suppressed by winds of over 12km/hr, but no clear suppression by low temperature was evident, at least until the beginning of October, when density of N. cincticeps became low. It was observed that N. lugens aduls to take off moved up to the top of rice plants and after take-off flew upright unless drifted by wind. The simultaneous take-off of many adults was observed. Sex-ratio (% of females) of take-off adults of N. lugens was about 20% in the beginning of each emergence period and tended to increase to 60%, representing 44.1% as an average. Almost the same trend was observed in N. cincticeps. No N. lugens that mated was captured among the flying 46 and 96 females at the peak period of each generation. These flights were considered to have the characteristics of migratory flights. © 1971, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.