Abstract: 【Aim】 To ascertain the effects of soil drought stress on the physiological metabolism, ovarian development and yolk protein content of Bradysia cellarum. 【Methods】 Reared respectively in the soil with the 10% relative water content (drought stress) and the 40% relative water content (wet treatment), the changes in the contents of key metabolites (soluble protein, fat, glycogen and trehalose) and the activities of the protective enzymes including superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in the 2nd and 4th instar larvae, and female and male adults of B. cellarum were determined, the ovaries of female adults were dissected and their developmental states were observed, and the relative contents of yolk protein and the expression levels of vitellogenin gene (Vg) in the 1-3-day-old pupae and adults were assayed.【Results】 Compared with the wet treatment, drought stress significantly reduced the water content and food intake of the 4th instar larvae of B. cellarum, for example, the food intake of the 4th instar larvae after the 48-h drought stress was 35.72% lower than that in the wet treatment. Under drought stress, the contents of soluble protein and fat in the 4th instar larvae and female adults significantly decreased, and the trehalose content significantly increased, as compared with those under wet treatment. Drought stress induced a significant increase in the activities of three protective enzymes, SOD, CAT and POD in the 4th instar larvae and female adults. Under drought stress, the SOD, CAT and POD activities in the 4th instar larvae increased by 31.64%, 18.69% and 48.61%, respectively, and those in the female adults increased by 34.13%, 12.67% and 31.35%, respectively, as compared with those in wet treatment. Drought stress inhibited the ovarian development and damaged the ovarian structure of female adults. Compared with the wet treatment, drought stress caused the content of yolk protein and the expression level of Vg in female adults to significantly decrease. The difference in the expression level of Vg in the 2-day-old adults between the two treatments was the most significant, and the expression level of Vg under drought stress decreased by 35.66% as compared with that under wet treatment. 【Conclusion】 B. cellarum can resist drought stress by regulating physiological metabolism. The decrease of yolk protein content is the main factor of fecundity decrease. This study provides a theoretical basis for control of B. cellarum with soil drought stress technology.

Key words: Bradysia cellarum, drought stress, energy substance, protective enzyme, yolk protein