Abstract: To ascertain the biological characteristics of the small brown planthopper, Laodelphax striatellus (Fallén), in Nanchang, Jiangxi, East China, the annual life history, the influences of temperature on development and reproduction, sex ratio and its overwintering biology were systematically investigated under laboratory and natural conditions. The results showed that this species exhibit mixed voltinism from 4 to 7 generations per year. Between 18 and 32℃, and 18 and 28℃, the egg duration and the nymphal duration gradually declined with increasing temperature, respectively. However, the nymphal duration was significantly longer at 30 and 32℃ than at 28℃. The duration of overwintering nymphs ranged from 143 to 187 d. The lower development thresholds of egg and nymph were 10.17℃ and 7.51℃, respectively. In the outdoors, the developmental duration of the 4th generation nymphs hatched at high temperature of mid-July had significantly delayed, showing high-temperature induced summer quiescence. Between 18 and 28℃, the pre-oviposition period gradually shortened with increasing temperature; however, the pre-oviposition period was longer at 30℃ than at 26 and 28℃. The oviposition period was the longest at 22℃, and the shortest at 30℃. The mean longevity of adults was the longest at 20-24℃. The number of nymphs produced per female was the highest at 28℃. Under both laboratory and natural conditions, the sex ratio is close to 1∶1. Between 18 and 32℃, the number of long-winged adults (macroptery) was significantly higher than that of short-winged adults (brachyptery). In the outdoors, the number of the brachytery was significantly more than that of the macroptery in the overwintering generation and the 6th generation, whereas the number of the macroptery was significantly more than that of the brachytery in other generations. Under natural conditions, winter diapause had already occurred in some individuals that hatched in mid-September, and all individuals that hatched after mid-October entered winter diapause. This planthopper overwintered as 1-5 instar nymphs. This study provides the basic data for the prediction of L. striatellus occurrence and the effective prevention and control of this pest.

Key words: Laodelphax striatellus, annual life cycle, temperature, developmental duration, fecundity, sex ratio, wing dimorphism, overwintering biology