In order to improve the rearing of Coccinella septempunctata L. (Coleoptera: Coccinellidae), nutrients such as shrimp, pollen, honey, and lard were added to the basic artificial diet, and the effects of the artificial diet on biological parameters and digestive enzymes were evaluated. The results show that beetles feeding on the supplemented diet exhibited pupation, emergence, fecundity, and hatching rates that were 102.69%, 125.02%, 162.33%, and 119.90% of those supplied with the basic diet, respectively. The addition of shrimp and pollen to the basal diet improved protease, trypsin, chymotrypsin, and aminopeptidase activity in larvae and female adults. The addition of lard improved lipase activity in female adults, and the addition of honey improved invertase activity in adults of both sexes. This study provides guidance for improving the nutritional benefits of ladybug artificial diets.

The insect predator Coccinella septempunctata can effectively control many types of pests, such as aphids, whiteflies, and small lepidopteran larvae. We previously found that C. septempunctata fed an artificial diet showed diminished biological properties(e.g. fecundity, egg hatching rate, survival rate, etc.) compared with those fed natural prey (Aphis craccivora), likely due to different nutritional characteristics of the diet. In this study, we used transcriptome sequencing analysis to identify nutrition- and metabolism-related genes of C. septempunctata that were differentially expressed depending on diet. The Illumina HiSeq2000 was used to sequence 691,942,058 total clean reads from artificial diet-fed and A. craccivora-fed C. septempunctata libraries, and the clean reads were assembled using Trinity de novo software (Tabel 2). Comparison of transcriptome sequences revealed that expression of 38,315 genes was affected by the artificial diet, and 1,182 of these genes showed a significant change in expression levels (FDR ≤ 0.05,|log2FC|≥1, “FC” stands for “fold change”). These differentially expressed genes (DEGs) were likely associated with the decreased egg laying capacity, hatching rate, longevity, and increased sex ratio (♀:♂) of adult C. septempunctata observed in the group fed the artificial diet. Furthermore, in the most DEGs metabolic pathways for C. septempunctata feeding on the artificial diet accumulated amino acid metabolic pathways, lipid metabolic pathways, and starch and glucose metabolism were down-regulated. We found some differentially expressed genes and metabolic pathways are related to nutrition, from which a more informative feedback for diet formulation was obtained and the artificial diet could be more efficiently optimized.

This study focuses on the regulatory effects of genes encoding the juvenile hormone (JH) receptor methoprene-tolerant (Met) and transcription factor krüppel homolog 1 (Kr-h1) on the reproductive capacity of Coccinella septempunctata male adults. Met and Kr-h1 expression levels were analyzed in males fed on artificial diets with and without JH by quantitative real-time PCR, and the effects of Met and Kr-h1 on male reproduction were analyzed by RNA interference technology. Met transcription levels in 5- and 10-day-old males fed with a JH-supplemented diet were lower than those without JH. Kr-h1 expression in 5-day-old adult males was lower in diets lacking JH but was higher in 10-day-old males fed on a diet lacking JH. There were no significant differences in the testes sizes of male ladybugs injected with Met-dsRNA when compared to GFP-dsRNA; however, the testis volume of ladybugs injected with Kr-h1-dsRNA was smaller than those injected with GFP-dsRNA. After males were injected with Met-dsRNA and Kr-h1-dsRNA, the mean egg production by females decreased by 12.75% and 23.10%, respectively, at 20 d postinjection. Our results show that Met and Kr-h1 have important roles in regulating reproduction by directly affecting testes development in males and egg production in females.

The potential role of the juvenile hormone receptor gene (methoprene-tolerant, Met) in reproduction of Coccinella septempunctata L. (Coleoptera: Coccinellidae)(Coleoptera: Coccinellidae), was investigated by cloning, analyzing expression profiles by quantitative real-time PCR, and via RNA interference (RNAi). CsMet encoded a 1518-bp open reading frames with a predicted protein product of 505 amino acids; the latter contained 2 Per-Arnt-Sim repeat profile at amino acid residues 30–83 and 102–175. CsMet was expressed in different C. septempunctata larvae developmental stages and was most highly expressed in third instar. CsMet expression in female adults gradually increased from 20 to 30 d, and expression levels at 25 and 30 d were significantly higher than levels at 1–15 d. CsMet expression in 20-d-old male adults was significantly higher than in males aged 1–15 d. CsMet expression levels in fat body tissues of male and female adults were significantly higher than expression in the head, thorax, and reproductive system. At 5 and 10 d after CsMet-dsRNA injection, CsMet expression was significantly lower than the controls by 75.05% and 58.38%, respectively. Ovary development and vitellogenesis in C. septempunctata injected with CsMet-dsRNA were significantly delayed and fewer mature eggs were produced. This study provides valuable information for the large-scale rearing of C. septempunctata.

The gene encoding juvenile hormone response (Krüppel homolog1, Kr-hl) in Coccinella septempunctata was investigated by cloning and analysing expression profiles in different developmental stages and tissues by quantitative real-time polymerase chain reaction (PCR). C. septempunctata Kr-hl (CsKr-hl) encoded a 1338 bp open reading frame (ORF) with a predicted protein product of 445 amino acids; the latter showed high similarity to orthologs in other species and contained eight highly-conserved Zn-finger motifs for DNA-binding. CsKr-hl was expressed in different developmental stages of C. septempunctata. The expression levels of CsKr-hl in eggs, 2nd, 3rd, 4th instar larvae, and pupa were 3.31, 2.30, 7.09, 0.58, and 7.48 times the number of 1st instar larvae, respectively. CsKr-hl expression levels in female adults gradually increased at 25–30 days and were significantly higher than expression at 1–20 days. CsKr-hl expression in 20–30 days-old male adults was significantly higher than males aged 1–15 days. CsKr-hl expression levels in heads of male and female adults were significantly higher than expression levels in the thorax, adipose, and reproductive system. Interestingly, CsKr-hl expression levels in the adipose and reproductive system of female adults were significantly higher than in adult male corresponding organs, which suggest that CsKr-hl plays an important role in regulating reproductive development in C. septempunctata.