What is the occurrence regularity of Robinia pseudoacacia (Plutella xylostella)?

The occurrence regularity of Robinia pseudoacacia (Plutella xylostella): one generation a year occurs in Hebei, Shandong, Jiangsu, Anhui and other places, and the mature larvae drill into the soil 10 to 15 cm deep to overwinter. Pupation began in the first and middle June of the following year. The pupal stage ranges from 10 to 15 days. The adult Eclosion occurred in the first and middle of July, and the peak of emergence was in the middle of July. The adults lie still in the branches and leaves during the day and begin to move in the evening, and the adults have phototaxis. Generally, eggs begin to lay eggs 3 hours after mating, and the eggs are mostly laid on the back of the leaves and a few on the front. The average number of eggs laid by each female is about 350. Adults for 7 to 10 days. The egg period is 6 to 8 days. The eggs began to hatch from mid-July to late July. The newly hatched larvae can spin and droop and spread the adjacent plants by the wind. The larval occurrence period is in the first and middle of August. The larvae have the habit of phototaxis and transplant harm. the 1st to 3rd instar larvae mostly live on the back of the leaves to avoid light and sleep during the day, feed at night, do harm to the whole day in overcast and rain, and only residual veins remain when the 3rd to 4th instar larvae feed. The larval stage is about 30 days. The mature larvae are generally buried in the middle of September to overwinter, and the worm body is in the shape of a horseshoe and lives in the soil.