Zeuzera leuconotum Butler(Lepidoptera: Cossidae) is one of the most damaging pests on forestry in northern China in recent years. Because its larvae cause damage by tunneling into tree trunks, it is very difficult to control by cutting off the damaged branches or applying insecticides. In order to find a pollution-free and efficient controlling method,we have already begun a series of studies on the sex pheromone of the pest. It is necessary to know the character of calling behavior and the circadian rhythm of sex pheromone production and release by female Z. leuconotum.
In this paper, the female moth calling behavior and characters were investigated through observation in the insectariums under the condition of (19-32)℃,75%-85% RH and 14L∶10D photoperiod. And the circadian rhythm of sex pheromone production and release by the female moth was researched in detail by determining the electrophysiological (EAG) responses. The crude extracts of sexual pheromone were prepared by the two methods. One of the methods was to directly extract pheromone from female sexual gland by hexane, and another was to collect pheromone from air in the bottle which filled with a female moth. The Former reflected the sex pheromone production, and the latter reflected the sex pheromone release.
The results showed that the calling behavior of all female moths occurred during the scotophase. Some females (43.3%) called on the first night after eclosion and called mainly during the second half of the scotophase. Calling varied with age of female. The percentage of females calling increased from 1 to 2-d-old and decreased from 3 to 6-d-old gradually. The percentage of 2-d-old females calling was the biggest (86.7%, average), significantly bigger than 1 or 4, 5, 6-d-old females(P＜0.05). The old females (5 to 6-d-old) called earlier than younger in the scotophase. The calling peak occurred in 4-6 h of scotophase.
The EAG response of males to different extracts reflected that only a few females could produce and release sex pheromone on the first night after eclosion. The sex pheromone production and release of females varied with age, which regulation was the same as that of calling. The sex pheromone production and release of 2-d-old females were the highest, significantly higher than those of other age females(P＜0.05). The sex pheromone production of the female gland increased with the time into scotophase, but very slowly from the onset to 4 h, and sharply from 4 to 5h, and peaked. After the peak, the production decreased greatly during 6 to 8h. At 4 h into scotophase, sex pheromone release began to increase, and quickly reached the peak. In a word, there was a circadian rhythm in the production and release of sex pheromone by Z. leuconotum. The peak of production occurred on 5 h into scotophase, but that of release occurred on 6 h of entering scotophase.
In the field test, it was found that the percentage of males trapped by using 2-d-old virgin females had the same regularity as mentioned above. Therefore, it was confirmed that the calling behavior, sex pheromone production and release of Z. leuconotum were synchronized.