Influence of host plants on growth，development and fecundity of natural enemy Picromerus lewisi

【Objective】The purpose of the study was to identify the effects of different host plants on the growth, development and reproduction of Picromerus lewisi,and to provide a scientific basis for efficient large-scale indoor breeding and field colonization of P. lewisi.【Method】 Under the indoor condition,the control group was provided with Tenebrio molitor pupa as food only,and the treatment group was provided with seedlings of Zea mays,Triticum aestivum, Phaseolus vulgaris,Pisum sativum as host plants in addition to T. molitor pupa,respectively,and the development and survival of P. lewisi nymphs were observed and recorded.The weight of P. lewisi was measured and compared between the growth stages(nymphs, male and female adults)on different host plants.The same day-age P. lewisi adults were fed and observed in a single pair,and the reproduction of P. lewisi was counted,including the preoviposition period and the number of eggs laid. The egg masses(over 30 eggs)were selected and incubated in plastic cups for observation, and the hatching rate of eggs and the time taken for 50% oviposition were counted.【Result】 There were no significant differences of different host plants on the longevity,frequency of egg laying by females,total number of eggs laid,hatching rate of egg masses and incubation period of P. lewisi adult(P>0.05),but the addition of plants improved or significantly(P<0.05) improved the survival rate of nymphs (except 1^stnymphs),increased the weight (except 2^ndnymphs),shortened the developmental and preoviposition period.P. lewisi nymph survival rates were higher in P. vulgaris and T. aestivum,86.67% and 83.33%,respectively,and the developmental periods were greatly shorter than that of Z. mays and P. sativum,27.52 d and 27.03 d respectively. P. lewisi adults had relaticely shorter preoviposition periods in P. vulgaris and T. aestivum,16.54 d and 16.31 drespectively; the single egg laying amounts were larger, 38.36 eggs and 36.30 eggs respectively,and a larger proportion of eggs were laid between 1-20 d after the start of oviposition,80.87% and 78.22% respectively.【Conclusion】 P. vulgaris and T. aestivum seedlings can effectively improve the growth,development and reproduction of P. lewisi,and can be used as host plants for large-scale artificial breeding of P. lewisi. In addition,P. vulgaris or T. aestivum can also be planted in the release field to facilitate the colonization of P. vulgaris.