Abstract: 【Aim】To explore the effects of oviposition season and geographical latitude on life history traits of the Japanese pine sawyer beetle, Monochamus alternatus, so as to provide a basis for the accurate prediction and management of this insect pest.【Methods】Six monitoring plots along the latitudinal gradient of about 1° in Jiangxi Province, Southeast China were established, then the generation differentiation and developmental duration were investigated by field pine tree trunk covering observation, and the overwintering larval instars were surveyed through dead wood dissecting.【Results】The 2nd generation differentiation of M. alternatus occurred in southern and central Jiangxi. The proportion of the differentiation entering the 2nd generation decreased from 45.75% to 2.46% in southern Jiangxi and from 17.42% to 0 in central Jiangxi with the delay of oviposition season, while there was only one generation in northern Jiangxi, where no generation differentiation occurred. The proportion of the eggs laid at the same month entering the 2nd generation decreased from 21.92% to 0 with increasing geographical latitude. The egg-pupal duration in differentiated and undifferentiated individuals in the forest was 110.66-122.01 and 330.61-366.01 d, respectively, and showed a latitudinal co-gradient variation and a counter-gradient variation, respectively. However, no significant difference was found in the developmental duration of differentiated and undifferentiated individuals. The overwintering larvae were at the 2nd-5th instars in southern and central Jiangxi and 4th-5th instars in northern Jiangxi, and the proportion of the 2nd instar overwintening larvae significantly decreased from 12.47% to 0 and the proportion of the 5th instar overwintering larvae significantly increased from 45.33% to 98.40% with increasing geographical latitude.【Conclusion】Oviposition season and geographical latitude have certain effects on the life history traits of M. alternatus, showing that oviposition season and geographical latitude significantly affect the generation differentiation proportion of this beetle, but not on the developmental duration of differentiated individuals and undifferentiated individuals. The larval instars and proportion of overwintering insects are obviously affected by geographical latitude.

Key words: Monochamus alternatus, generation differentiation, developmental duration; overwintering instars, seasonality, latitudinal gradient