Abstract:

Objective: In this study, the emergence, courtship and mating behavior of Dendrolimus suffuscus illustratus were investigated to explore its law of courtship and mating, and the attraction activity between male and female moths was tested through the experiment of trapping moths in the forest. This study aims to lay a foundation for the extraction and identification of sex pheromone of D. suffuscus illustratus. Method: This experiment was conducted in 2019 and 2020 to observe the eclosion and reproductive biological rhythm of D. suffuscus illustratus by artificially rearing in outdoor cages and trapping moths in the field. Result: The results showed that adult eclosion was concentrated in the dark period (19:00-2:00), and the daily eclosion peak was concentrated at 21:00. The eclosion period in 2019 was different from that in 2020. In 2019, the pupae in the cage began to emerge in early July, and reached the peak in late July (around July 29), and gradually decreased in mid-August. In 2020, the pupae in the cage emerged later than that in 2019, and began to emerge in mid-July, and entered the peak in mid-August (around August 11), and then gradually decreased. The number of emerged male moths was more than that of emerged female moths before the emergence peak, while the number of female moths was more than that of male moths after the peak. The emergence rates of adults in 2019 and 2020 were 83.8% and 88.5%, respectively. The sex ratio of male and female moths was 1∶1.04 (2019) and 1∶1.01 (2020). The average life span of unmated male and female moths was 4.05 and 5.84 d, respectively, and the average life span of mated female and male moths was 3.69 and 5.33 d, respectively. The courtship behavior of female moths was observed on the day of eclosion. The courtship behavior occurred in the dark period. The highest courtship rate of 1-day-old and 2-day-old adults was 40% and 45.5% respectively during the 6-8 h of the dark period. With the increase of age, the courtship behavior was advanced and the courtship rate decreased gradually. The rhythm of mating and courtship was consistent. The mating rate of 2-day-old adults was the highest (45%) at 6-8 h in the dark stage. With the increase of age, the mating behavior was advanced and the mating rate decreased. Both mated and unmated females were able to lay eggs. After mating, the average number of eggs laid by females was 154.1, and the average hatching rate was 94.8%. The average number of eggs laid by unmated females was 160.7 and the hatching rate was 0. The results showed that virgin moths could attract male moths in the field. The number of male moths trapped by 2-day-old virgin moths was significantly higher than that by other female moths. However, neither the blank trap nor the male moth attracted the adults. Conclusion: The emergence and reproductive behavior of D. suffuscus illustratus have obvious time rhythm. The day age is one of the main factors affecting the behavior of courtship and mating. With the increase of age, the time of courtship and mating is advanced, and the courtship rate and mating rate decrease.

Key words: Dendrolimus suffuscus illustratus, emergence, courtship, mating, field trap