The Aphelinus asychis female adult is an important arrhenotocous parthenogenesis parasitoid of Myzus persicae, and its reproductive mode is beneficial for the population continuation of A. asychis by way of multiple mating and backcross. To explore the effect of mating on the population fitness and control efficiency of A. asychis, its mating frequency and backcross were observed under laboratory conditions. The results showed that most matings in A. asychis involved four distinct stages: courtship, pre-copulatory, copulation, and post-copulatory behaviours. Only the duration of courtship increased significantly with an increase in copulation frequency for females, and the courtship duration of A. asychis females mated with different males were significantly shorter than those mated with the same male at the same mating times, which suggested that A. asychis females might prefer to mate with different males to enrich the genotype of their offspring. The total number of mummified aphids and the female and male longevity decreased significantly with an increase in mating frequency. On the contrary, female progenies increased significantly with an increase of mating frequency, suggesting that sperm limitation might occur in females when they only mated once. These results imply that females might prefer to receive more sperm by mating multiple times in their life span. In addition, we found that the intrinsic rate of increase (r) of A. asychis of the control group (0.2858 d⁻¹) was significantly greater than that in the backcross treatment (0.2687 d⁻¹). The finite killing rate (θ) of A. asychis of the control group was similar to that in the backcross treatment, which showed that this treatment had a negligible negative effect on the control efficiency of A. asychis. In conclusion, the results showed that multiple mating increased the number and proportion of A. asychis female progenies but shortened the longevity of female and male adults, while the negative effect of backcross on the control efficiency of A. asychis was negligible.

Aphelinus asychis, a polyphagous parasitoid, has been widely used as an efficient biological control agent against the aphid Myzus persicae. Aiming to evaluate the influence of temperature on the biological characteristics and control potential of A. asychis for M. persicae, we compared the life table parameters and control potential of A. asychis, which included the developmental time, longevity, fecundity, intrinsic rate of increase (r), and finite killing rate (θ). The results showed that increasing the temperature significantly decreased the developmental time and longevity of A. asychis. The r at 24 (0.2360 d⁻¹) and 28 °C (0.2441 d⁻¹) were significantly greater than those at 20 (0.1848 d⁻¹) and 32 °C (0.1676 d⁻¹). The θ at 24 (0.4495), 28 (0.5414), and 32 °C (0.4312) were also significantly greater than that at 20 °C (0.3140). The relationship between population fitness (r and θ) and temperature followed a unary quadratic function (R² > 0.95). The temperatures for the expected maximum intrinsic rate of increase (r_max) and the maximum finite killing rate (θ_max) were 25.7 and 27.4 °C, respectively. In conclusion, A. asychis could develop and produce progenies within the temperature range of 20–32 °C, and its control efficiency for M. persicae at 24, 28, and 32 °C was greater than that at 20 °C. The most suitable temperature range for controlling M. persicae with A. asychis in the field might be between 25.7 and 27.4 °C.

Degreased Hermetia illucens (black soldier fly) meal has been widely used as a substitute for traditional protein sources, including fish and soybean meals, in livestock and aquaculture especially for prawn Litopenaeus vannamei and Macrobrachium rosenbergii . The oriental river prawn ( Macrobrachium nipponense ) is a commercially significant shrimp species prevalent in freshwater lakes and river systems across China. We explored the potential of replacing fish meal with degreased H. illucens meal in the diet of M. nipponense by assessing how different substitution ratios and the freshness of the meal influenced river prawn growth. The results showed that a 20% substitution ratio significantly increased the specific growth rate and condition factor of M. nipponense ( p < 0.05), while the feed conversion ratio was significantly reduced ( p < 0.05). Based on the dose–response model, the specific growth rate reaches its peak when the substitution ratio is 24.25%. At this 20% ratio, there was a significant increase in the crude protein and lipid content in M. nipponense muscle. Moreover, the concentrations of several essential amino acids, along with monounsaturated and polyunsaturated fatty acids, were notably elevated compared to the control group ( p < 0.05). In the 20% substitution group, the activities of superoxide dismutase, trypsin, and lipase in the hepatopancreas, as well as acid phosphatase and lysozyme in the hemolymph, were significantly increased relative to the control group ( p < 0.05). The research also assessed the impact of using moderately decomposed (T ₁ : TVB‐N 65 mg/100 g) and highly decomposed (T ₂ : TVB‐N 80 mg/100 g) degreased H. illucens meal as a 20% replacement for fish meal, in comparison to fresh degreased H. illucens meal (TVB‐N 50 mg/100 g). In the T ₁ group, both the specific growth rate and feed conversion ratio were considerably lower than those observed in the control group ( p < 0.05). In both the moderately (T ₁ ) and highly (T ₂ ) decomposed treatment groups, the crude lipid content in M. nipponense muscle was significantly reduced, while the crude ash content was notably higher than that in the control group ( p < 0.05). Additionally, the T ₁ and T ₂ groups exhibited significantly decreased levels of certain essential amino acids, saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, and mineral elements in the muscle ( p < 0.05). In these groups, the activities of alanine aminotransferase in the hepatopancreas and hemolymph, as well as the malondialdehyde content in the hepatopancreas, were significantly elevated compared to the control group ( p < 0.05). On the other hand, the activities of hepatopancreatic trypsin and lipase in the T ₂ treatment were significantly reduced compared to the control group ( p < 0.05). In conclusion, we recommend the use of fresh degreased H. illucens meal at a substitution level of 20%–25% (with the model‐derived peak near 24.25%) in M. nipponense diets.