Abstract:

【Aim】 Cyanopterus ninghais is an unexplored parasitoid wasp that mainly parasitizes late instar larvae of Monochamus alternatus. To effectively develop the biocontrol potential of C. ninghais and utilize it in biological control of M. alternatus, the biological characteristics of C. ninghais adults were studied. 【Methods】 The eclosion rhythm, mating behavior and parasitization process of C. ninghais adults were observed and recorded through multi-generation rearing in the laboratory. The effect of female mating on the parasitism and reproductive modes of C. ninghais adults were studied by investigating the parasitism rates, offspring numbers and sex ratios in different mating conditions. The host selection of female adult of C. ninghais on M. alternatus at different larval instars and pupa was determined through choice and non-choice tests. Additionally, the adult longevity of C. ninghais was also examined under different nutritional conditions (no feeding, fed with purified water and fed with 20% honey solution). 【Results】 C. ninghais adults eclosed mainly from 6:00 to 12:00, and the eclosed adults accounted for 61.00% of the total eclosed adults. The mating process could be divided into four stages: courtship, precopulation, copulation and postcopulation. The peak mating time was from 17:00 to 21:00. Females mated only once in their lifetime, while males mated multiple times and there was mating competition among males. The parasitization process could also be divided into four steps: host-seeking, host-checking, ovipositing, and carding after completion. The unmated female adult produced only male offspring, while the ratio of female to male produced by mated female adult was 1︰1. C. ninghais was able to parasitize M. alternatus larvae at the 2nd-5th instars, with a strong preference for the 3rd instar larvae. The adult longevity of C. ninghais increased significantly when supplementing nutrition. Both female and male adults of C. ninghais survived the longest days, (35.50±3.31) and (20.80±2.00) d, respectively, when feeding 20% honey solution. 【Conclusion】 C. ninghais is an idiobiont-ectoparasitoid, and could perform both bisexual and parthenogenetic reproduction. The eclosion and mating of C. ninghais adults have obvious circadian rhythm, and they prefer to parasitize the 3rd instar larvae of M. alternatus. Providing honey solution can significantly prolong the longevity of C. ninghais adults. Overall, these findings suggest that C. ninghais has promising potential for further development and application in the biological control of M. alternatus.

Key words: Cyanopterus ninghais; Monochamus alternatus, biology, biological control, parasitism, mating