【目的】 棉蚜Aphis gossypii是一种重要的农业害虫，日光蜂Aphelinus mali作为蚜虫的关键天敌，在生物防治中应用广泛。为评估日光蜂对棉蚜的防治潜能，本研究分析了不同龄期棉蚜对其的寄生适应性，并比较了2龄与4龄棉蚜混合种群中，该蜂对不同龄期个体的选择差异。【方法】 在实验室条件下，采用小叶碟饲养法评估寄生于不同龄期棉蚜的日光蜂子代发育历期、羽化率、性比、寿命和后足胫节长度；采用观察法评估并记录日光蜂雌蜂在2龄和4龄混合棉蚜小叶碟中30 min的行为；采用解剖法评估雌蜂在混合龄期棉蚜小叶碟中24 h内的产卵和取食数量。【结果】 寄生于所有龄期棉蚜若蚜的日光蜂子代均能完成生长发育，随寄生时棉蚜龄期的增加，寄生率显著降低（P<0.001），发育历期和后足胫节长度均显著增加（P<0.001），子代雌蜂比例随棉蚜龄期的增加而增加，但影响不显著（P=0.081），日光蜂成虫寿命无差异（雌蜂：P=0.074；雄蜂P=0.411）。选择性试验中，日光蜂寄生2龄棉蚜的数量显著多于4龄（P<0.001），但取食不同龄期蚜虫数量并无明显的差异（P=0.468）。【结论】 寄生低龄期棉蚜，日光蜂发育历期更短，羽化率更高；寄生高龄期棉蚜，日光蜂个体更大，雌蜂比例更高。相较4龄棉蚜，日光蜂偏好寄生2龄棉蚜。本研究明确了日光蜂在以棉蚜为寄主时的寄生和取食龄期的适宜性及选择偏好，为日光蜂的人工饲养提供了依据，有利于日光蜂在蚜虫生物防治中的应用。

 [Aim]  To investigate the potential of using the wasp Aphelinus mali as a biological control for Aphis gossypii, an important agricultural pest, more specifically, the relative preference of Aphelinus mali for different Aphis gossypii instars. [Methods]  The leaf disc rearing method was used to determine the developmental duration, emergence rate, sex ratio, longevity, and hind tibia length of Aphelinus mali offspring parasitizing different Aphis gossypii instars in a laboratory. The behavior of female Aphelinus mali was observed and recorded for 30 min on leaf discs with 2nd and 4th instar Aphis gossypii. Dissection was employed to evaluate the number of eggs laid, and aphids consumed, by female wasps within 24 h. [Results]  Offspring of Aphelinus mali were able to complete their development by parasitizing all Aphis gossypii instars. However, parasitism of older Aphis gossypii instars was significantly less than that of younger instars (P<0.001), and both the developmental duration and hind tibia length of Aphelinus mali that parasitized older instars were significantly longer (P<0.001). The proportion of female offspring produced tended to increase with host instar, but this difference was not statistically significant (P=0.081). No significant difference was found in the adult longevity of Aphelinus mali (females: P=0.074; males: P=0.411). In choice tests, although female Aphelinus mali parasitized significantly more 2nd than 4th-instar aphids(P<0.001), no such preference was apparent with respect to predation (P=0.468). [Conclusion]  Parasitizing younger aphid instars resulted in shorter developmental duration and higher emergence rates for Aphelinus mali, whereas parasitizing older instars produced larger wasps with a higher proportion of females. Aphelinus mali preferred to parasitize 2nd over 4th instar Aphis gossypii. These results clarify the oviposition and feeding preferences of Aphelinus mali for different instars of Aphis gossypii, providing useful information for the mass rearing of Aphelinus mali and facilitating the application of this species as a biological control for aphids.