Abstract: ating behavior and capacity in the beet armyworm, Spodoptera exigua (Hübner) were investigated under laboratory conditions (27℃ ±1℃, L14∶D10). The results indicated that both males and females were able to mate on the first night, and all males and females observed completed their mating on the second night after emergence. The mating rates on the first three nights were relatively high (>82%), and decreased significantly after the fourth night (<50%). Daily mating activity occurred from 23:15 to 05:30, and peaked from 01:30 to 02:30 and from 03:00 to 04:00, with a higher frequency in the first peak. Mating duration of the moths lasted from 30 to 60 minutes (40.8%, n=97), followed by 60 to 90 minutes (19.4%), and in some cases (10.2%) lasted more than 180 minutes. Furthermore, mating durations were highly associated with the moth age: in the older moths it lasted significantly longer than in the younger ones. Lifetime mating number for a male was from 1 to 11, with an average of 50 However, mating capacity of a male was significantly associated with operational sex ratio. The lifetime mating number of males was only 3.0 in average when a male was confined with one female, but increased to 5.1-6.0 when a male was confined with 2-5 females. On the other hand, the percentage and frequency of female mated were also tied to sex ratio. This could be demonstrated by the fact that the percentage of unmated female increased from 8.3% to 32%, and oncemated females from 16.7% to 38.7%, at a sex ratio of 1:1 and 1♂:5♀, respectively, whereas the proportion of females that mated more than 5 times decreased from 25% to 0 under the same conditions. The significance of these findings for the application of sex pheromones to control the beet armyworm was discussed.

Key words: Spodoptera exigua, mating behavior, mating capacity, sex ratio, matin g duration, sex pheromone