Effects of male-biased sex ratios on the reproduction and offspring development of the predatory mirid bug, Cyrtorhinus lividipennis (Hemiptera: Miridae)

Author of the article:XU Yi-Jie WANG Ying LIU Fang HU Kui

Author's Workplace：College of Plant Protection, Yangzhou University

Key Words：Cyrtorhinus lividipennis; sex ratio; fecundity; offspring development

Abstract：[Aim]  To clarify the effects of a male-biased sex ratio on the fecundity and development of offspring of the predatory mirid bug Cyrtorhinus lividipennis, and to promote the large-scale breeding of this species as a biological control for rice planthoppers and rice leafhoppers. [Methods]  We conducted an experiment to examine the effects of a male-biased parental sex ratio (female: male ratios of 1∶1, 1∶2, and 1∶3) on various reproductive parameters, including pre-oviposition period, fecundity (eggs laid per female), oviposition duration, as well as egg hatchability, nymph developmental duration, emergence rate, sex ratio and adult lifespan, of offspring. [Results]  The pre-oviposition period (F = 1.239, df = 2,57, P = 0.297 3), egg hatchability (F = 1.883, df = 2,57, P = 0.161 5), offspring emergence rate (F = 0.047, df = 2,12, P = 0.9541) and sex ratio (F = 0.815, df = 2,12, P = 0.465 9) were not significantly affected by the parental sex ratio. However, compared to the control population [1∶1 sex ratio, (115.65±30.49) grain/female], the fecundity of a population with a 1∶3 sex ratio was significantly higher [(137.15±32.29) grain/female; 18.59%] (LSD = 2. 350, df = 57, P = 0.022 2). Nymphs from populations with sex ratios of 1∶2 [(11.25±1.65) d ] and 1∶3 [(11.11±1.13) d] had prolonged developmental durations of 1.18 (LSD = 3.518, df = 97, P = 0.000 7) and 1.05 d (LSD = 3.205, df = 97, P = 0.001 8), respectively. Furthermore, the lifespan of the offspring of a population with a 1∶2 sex ratio was 3.52 d (LSD = 2.980, df = 45, P = 0.004 6) longer for female adults [(18.80±2.11) d] and 2.64 d (LSD = 2.061, df = 49, P = 0.044 6) longer for male adults [(17.41±4.12) d] compared to the control population [female: (15.28±3.29) d, male: (14.77±3.14) d]. [Conclusion]  These results indicate that a male-biased sex ratio has positive effects on the fertility and offspring development of C. lividipennis.