Abstract: 【Aim】 To study the parasitism of Psyllaephagus arenarius on Poratrioza sinica， so as to provide the scientific basis for wise use of P. arenarius to control P. sinica.【Methods】 The morphological and parasitic characteristics of P. arenarius were observed in the laboratory， the parasitism preference， parasitism functional response， mutual interference and host discrimination of P. arenarius wasps on P. sinica nymphs were assessed through the laboratory  experiments， and the parasitic characteristics of this parasitoid in the field was also investigated in Zhongning， Ningxia， northwestern China. 【Results】 The results showed that P. arenarius is both solitary and endoparasitoid. P. arenarius preferred to parasitize on the 4th instar nymphs of P. sinica rather than on the 3rd and the 5th instar nymphs， with the preference coefficient of 0.44±0.02， while did not parasitize on the 1st and 2nd instar nymphs. The maximum parasitic amount， searching efficiency，processing time of P. arenarius on the 4th instar nymphs of P. sinica were 40.3， 0.8688 and 0.0243， respectively. The coefficient of mutual interference of P. arenarius within species was 0.3856， and P. arenarius wasps had significant host discrimination. The occurrence of P. arenarius lasted from late June to mid September， which overlapped with that of the 3rd-5th instar nymphs of the 2nd generation of P. sinica. The average parasitism rate of P. arenarius was 44.2%±6.7%， and the maximum parasitism rate (89.7%±12.2%) happened on 4 July. The parasitism rates of P. arenarius were the highest at lower hierarchy of plants (58.1%±6.8%) among three hierarchies of plants， in the west of plants (51.4%±8.2%) among five directions and on the 4th instar nymphs of P. sinica (69.7%±3.1%) among different larval instars. 【Conclusion】 The results suggestthat P. arenarius is one of parasitic natural enemies with the potential to control P. sinica， and artificial releasing of this parasitoid， a newly recorded species in China， might effectively control P. sinica nymphs and alleviate their damage in the field.

Key words: Psyllaephagus arenarius, Poratrioza sinica, Lycium chinense, parasitic characteristics, parasitism preference, parasitism functional response, mutual interference, host discrimination