Effects of temperature on reproduction and development of Cyanopterus ninghais (Hymenoptera: Braconidae), a larval parasitoid of Monochamus alternatus (Coleoptera: Cerambycidae)

Cyanopterus ninghais (Hymenoptera: Braconidae), a newly discovered gregarious ectoparasitoid, is a promising biological control agent against the third-fifth instar larvae of the Japanese pine sawyer, Monochamus alternatus (Coleoptera: Cerambycidae). Effects of constant ambient temperatures (17, 20, 23, 26, 29, and 32 ℃) on the reproduction and development of the parasitoid were determined in the laboratory. We investigated the reproductive parameters of C. ninghais, including the pre-oviposition period, parasitism rate, offspring number, emergence rate, and sex ratio, at these six temperatures using 4th-instar larvae of M. alternatus as hosts, and the developmental duration of each developmental stage (egg, larva, and pupa) and generation at six temperatures was also measured. The pre-oviposition periods of C. ninghais decreased gradually with increasing temperatures. Both the parasitism rates and the number of offspring exhibited a parabolic trend in relation to increasing temperatures. Temperature did not significantly affect the emergence rate and sex ratio of progeny. The duration of each developmental stage was inversely correlated with temperature within the range of 20 to 32 ℃. We concluded that temperatures in the range of 26 to 29 ℃ are the most suitable for the development and reproduction of C. ninghais. These findings provide important information for improving the artificial rearing efficiency and field release of this parasitoid under different temperature conditions.