Biological and Biochemical Impacts of Temperature on Spodoptera littoralis (Boisduval)

Background: The Egyptian cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae), is one of the most destructive agricultural lepidopteran pests in Egypt, attacking several important crops all year round. S. littoralis can have two to seven generations per year, depending on the climate of the region; for example, changes in temperature affect all life processes of S. littoralis. Methods: The development, survival, and fecundity of S. littoralis at one of five constant temperatures as well as their effects on the biochemical impacts were investigated. Results: The results showed that the duration of developmental stage (eggs, instars, pupae), longevity, and fecundity significantly decreased with increasing temperature from 15 to 35 oC. Larvae emerged fastest from the eggs at 25 °C. The percentage of oviposited females was 46, 58, 74.5, 66.5, and 50% at 15, 20, 25, 30, and 35 °C, respectively. The results also showed that the fourth larval instars of S. littoralis at 25 oC had a higher level of proteins, lipids, carbohydrates, and free amino acids in comparison with those larvae at 35 oC. Therefore, temperature rise leads to increasing metabolic rate, and decreasing the development period. Conclusion: Thus, 25 °C was the optimum temperature for development, fecundity, rates of biochemical and physiological reactions of S. littoralis.