Molecular Entomology, 2025, Vol.16, No.1, 11-18 http://emtoscipublisher.com/index.php/me 14 changes. Each pupa was placed in sterilized sand for pupation, and the pupal length was measured 24 hours after pupation (Jun and Hong, 2005). To prevent dryness from causing abnormal pupation, the pupae were considered for transfer to moist sand or petri dishes to maintain humidity. 3 Results and Analysis 3.1 Duration from Pupa to Pupa The experiment recorded the complete generation development cycle of Spodoptera litura under artificial control environment (temperature of about 25.5 ℃, humidity of 23%, natural light cycle). The average developmental period from the first generation pupae to the second generation pupae is about 45 days (45.2 ± 2.1 days), specifically manifested as a pupal period of about 15 days (15.3 ± 0.8 days), an adult oviposition period of about 2 days (2.1 ± 0.3 days), an egg period of about 4 days (4.2 ± 0.5 days), and a larval period of about 24 days (23.6 ± 1.7 days). Compared with the growth cycle (38-39 days) reported in literature for natural feed such as green vegetables and Chinese cabbage, the development period under soybean feeding conditions is significantly prolonged (Figure 1) (Ramaiah and Maheswari, 2018; Hashmi et al., 2023). Figure 1 The four developmental stages of Spodoptera litura: egg, larva, pupa and adult The overall observation results indicate that the larval stage occupies more than half of the entire life cycle and is the stage with the most significant changes in energy consumption and growth rate. The entire process is slightly longer than other natural feed sources such as cabbage and green vegetables (the incubation period of Spodoptera litura on cabbage is about 37~40 days) (Mao et al., 2008). Under experimental conditions, the lifespan of adult insects is relatively short (about 4 days), which may be related to the low air humidity in the experimental environment (the optimal humidity is around 75%). Low humidity poses challenges to the smooth emergence of pupae and the survival of adult insects (Wei et al., 2008). A total of 132 insect pupae were collected in the experiment, which increased by about 10 times compared to the first generation of 13 insect pupae, demonstrating a certain level of reproductive ability. However, compared to other studies that achieved a reproductive efficiency of more than 20 times under optimized humidity conditions (60-80%), the reproductive effect of this experiment is still relatively low, which further confirms that humidity is an important factor affecting its developmental success rate (Sun et al., 2015). Spodoptera litura larvae are highly sensitive to both food quality and quantity. In this experiment, when the rearing density was too high or soybean plants were insufficient, cannibalistic behavior among larvae was commonly observed. Abnormal behaviors during the larval stage, such as fighting and pseudo-death falls, could also affect their developmental efficiency. Tu et al. (2010) recommended implementing individual separation strategies under high-density rearing to reduce stress and mortality. 3.2 Gender differences in pupae In this experiment, the most intuitive "genital observation method" was used to distinguish the male and female characteristics of 13 experimental armyworm pupae in order to evaluate their sex characteristics. The results showed that the genital area of male pupae usually presents obvious protrusions with a dark brown color, while
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