Acta Entomologica Sinica

Effect of piwi knock-down on hemocyte proliferation and differentiation in Drosophila melanogaster

LIU Xiao-Nan, ZHAO Su-Juan, WANG Bo, WANG Hong-Xin, HAO Yang-Guang

2021, 64(12): 1359-1366. doi:10.16380/j.kcxb.2021.12.001

Abstract ( 166 )

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【Aim】 To explore the effect of piwi knock-down on hemocyte proliferation and differentiation in Drosophila melanogaster. 【Methods】 The D. melanogaster strains e33C-Gal4 and Hml-Gal4-UAS-2×EGFP were crossed with the wild strain w¹¹¹⁸ and the strain UAS-piwi RNAi, respectively, to reduce the expression of piwi gene in circulating hemocytes or lymph glands of D. melanogaster. The localization of Piwi protein in hemocytes and its effect on hemocyte proliferation and differentiation in D. melanogaster were detected by immunofluorescence staining. 【Results】 Piwi protein was expressed in circulating hemocytes and the whole lymph glands of D. melanogaster, and was mainly localized in the cytoplasm. The knock-down of piwi gene resulted in significant increase in the number of circulating hemocytes and the number of cells in the M phase of mitosis, but the differentiation of plasmatocytes and lamellocytes in circulating hemocytes were not affected. The knock-down of piwi gene had no effect on the proliferation of lymph gland hemocytes, but resulted in the excessive differentiation of plasmatocytes and the generation of lamellocytes. 【Conclusion】 The knock-down of piwi gene in circulating hemocytes in Drosophila can induce the overproliferation of hemocytes, while the knockdown of piwi gene in lymph glands can induce abnormal differentiation of hemocytes.

Knockout of ebony gene leads to melanin pigmentation in the rice stem borer, Chilo suppressalis (Lepidoptera: Crambidae) (In English)

SUN Hao, HUANG Jing-Mei, LIU Yan, GE Wen-Chao, WANG Shuai, YANG Feng-Xia, GAO Cong-Fen, WU Shun-Fan

2021, 64(12): 1367-1376. doi:10.16380/j.kcxb.2021.12.002

Abstract ( 336 )

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【Aim】 The rice stem borer, Chilo suppressalis, is a destructive rice pest in China and other Asian countries. However, due to lack of genetic tools, the functional genomic studies in C. suppressalis are seriously constrained. The aim of the study is to use a marker gene, ebony, to establish a gene editing system based on CRISPR/Cas9 technology in C. suppressalis. 【Methods】 With the amino acid sequences of Bombyx mori ebony protein as a query, the putative C. suppressalis ebony gene was obtained on its genomic database by the TBLASTN program. The full-length cDNA of ebony gene of C. suppressalis was cloned by PCR and subjected to bioinformatical analysis. The expression patterns of Csebony at different developmental stages (egg, larval, pre-pupal, pupal, and male and female adult stages) and in multiple tissues (head, epidermis, fat body, gut, and Malpighian tubules) of the 4th instar larvae of C. suppressalis were analyzed by qRT-PCR. Finally, we performed targeted knockout of ebony gene in C. suppressalis by microinjecting the ribonucleoprotein complexes specific guide RNA/Cas9 protein into the newly laid eggs within 2 h based on the CRISPR/Cas9 gene editing technology. 【Results】 The full-length cDNA of Csebony gene (GenBank accession no.: MZ846208) of C. suppressalis was cloned. It contains a 2 586 bp ORF encoding 861 amino acids, with the molecular mass of 9.5 kD and theoretical isoelectric point of 5.10. Csebony has no signal peptide sequence at the N-terminus. Domain analysis showed that Csebony has three conserved domains. Phylogenetic analysis indicated that Csebony is most closely related to Ostrinia furnacalis ebony. The qRT-PCR results showed that Csebony was highly expressed in the pupal stage and head. Knockout of Csebony caused melanin pigmentation in larvae, pupae, and adults of C. suppressalis. 【Conclusion】 The results showed that Csebony is involved in regulating cuticle pigmentation of C. suppressalis, and CRISPR/Cas9-based genome editing technology is effective in C. suppressalis. We can use visible marker gene to establish CRISPR/Cas9-based genome editing system in non-model organisms, so as to offer a valuable genetic tool for the study of functional genomics in C. suppressalis.

Effects of nutrition on the growth and reproductive signaling pathways in the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae)

KANG Kui, CAI Yong-Jin, ZHANG Dao-Wei, GONG Jun, ZHANG Wen-Qing

2021, 64(12): 1377-1387. doi:10.16380/j.kcxb.2021.12.003

Abstract ( 118 )

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【Aim】 Insects perceive external nutritional status, and nutritional signals in vivo are transmitted through many signal pathways to regulate insect growth and reproduction. This study aims to tentatively explore the molecular mechanism of nutritional regulation on the growth and reproduction of the rice brown planthopper, Nilaparvata lugens. 【Methods】 The day-2 3rd instar nymphs of N. lugens were fed to adults under different nutrient conditions ［fed with 100% artificial diet (pure artificial diet D-97, the control), 50% artificial diet and 25% artificial diet, respectively］, and the body weight, developmental duration, survival rate and number of mature eggs per ovary were counted. Then, the relative expression levels of IIS, TOR and AMPK signaling pathway related genes (InR1, InR2, AKT, FoxO, TOR, S6K, 4EBP, AMPKα, AMPKβ and AMPKγ) in different tissues (ovary, body fat and other tissues) of the 2-day-old adults were detected by quantitative PCR, and the phosphorylation levels of Akt, FoxO and AMPK in the ovary and other tissues of the 6-day-old adults were detected by Western blot. Meanwhile, the ROS levels in different tissues of the 6-day-old adults and the titers of juvenile hormone (JH) and 20-hydroxyecdysone (20E) in N. lugens at different developmental stages were also detected. 【Results】 Compared with the control fed with 100% artificial diet, the artificial diet of lower concentrations resulted in a significant decrease in body weight from the day-2 5th instar nymph to adult, shortened developmental duration from day-2 3rd instar nymphs to adult, an increased mortality, and a significant decrease in the number of mature eggs per ovary of N. lugens. The expression levels of IIS, TOR and AMPK signaling pathway related genes InR2, TOR, 4EBP and AMPKα in the ovary, body fat and other tissues, AKT, S6K and AMPKγ in the fat body and other tissues, and InR1, FoxO and AMPKβ in the other tissues of the 2-day-old adults fed with the artificial diet of lower concentrations decreased significantly as compared to those in the control, while those of InR1, AKT, FoxO, and AMPKγ in the ovary were relatively stable. The phosphorylation levels of AKT, FoxO, and AMPK in the ovary and other tissues of the 6-day-old adults fed with the artificial diet of lower concentrations were significantly increased as compared with those of the control. With the decrease of nutrient concentration in the artificial diet, the ROS levels in different tissues of the 6-day-old adults increased significantly as compared to that in the control. The JH titers in the day-2 4th instar nymphs under different nutrient conditions showed no significant difference, while the JH titers in the day-2 5th instar nymphs and 2-day-old adults under low nutrient conditions were significantly decreased and increased, respectively, as compared to those in the control. Low nutrient conditions resulted in a significant increase in 20E titer both in nymphs and adults. 【Conclusion】 Under conditions of nutrient deficiency, the expression levels of key genes in the nutritional signal transduction pathways including IIS, TOR and APMK pathways in N. lugens decrease, while the ROS level significantly increases, and the biosynthesis of JH and 20E is affected by regulating the phosphorylation levels of AKT, FoxO and AMPK.

Role of a C-type lectin, RfCTL-S1, in immune defense in larvae of the red palm weevil, Rhynchophorus ferrugineus (Coleoptera: Dryophthoridae)

LU Sheng-Ping, LIU Hui-Hui, SU Zhi-Ping, LIU Qian-Xia, HOU You-Ming, SHI Zhang-Hong

2021, 64(12): 1388-1397. doi:10.16380/j.kcxb.2021.12.004

Abstract ( 61 )

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【Aim】 This study aims to determine the role of a C-type lectin, RfCTL-S1, in immune defense in larvae of the red palm weevil, Rhynchophorus ferrugineus. 【Methods】 The sequence characteristics of RfCTL-S1 of R. ferrugineus were analyzed by bioinformatics methods. The expression levels of RfCTL-S1 across the different tissues (head, integument, foregut, mid-/hindgut, hemolymph and fat body) of the 4th instar larvae of R. ferrugineus were assayed by RT-qPCR. The abundance of RfCTL-S1 transcripts in the fat body and gut of the 4th instar larvae of R. ferrugineus challenged with Escherichia coli DH5α and Staphylococcus aureus by injection with 1 μL bacterial suspension with the OD₆₀₀ value of 1.6 was also detected by RT-qPCR. Moreover, the expression levels of the antimicrobial peptide genes, including RfAttacin, RfCecropin, RfColeopericin and RfDefensin, in the fat body and gut of the 4th instar larvae of R. ferrugineus after RNAi of RfCTL-S1 were also quantified by RT-qPCR. After RfCTL-S1 was silenced by RNAi, the ability of R. ferrugineus individuals to clear the invaded EGFP-tagged E. coli in the hemolymph and the number of cultivable bacterial colonies in the gut of the 4th instar larvae of R. ferrugineus were evaluated. 【Results】 The bioinformatics analysis revealed that RfCTL-S1 contains a signal peptide and the carbohydrate recognition domain (CRD) with EPN motif, but without transmembrane domain, suggesting that RfCTL-S1 is a secretory protein with mannose-binding activity. RT-qPCR results showed that RfCTL-S1 was highly expressed in the hemolymph of the 4th instar larvae of R. ferrugineus. In the fat body of R. ferrugineus larvae at 24 h after injection of E. coli, the expression level of RfCTL-S1 was significantly down-regulated as compared with that of the control injected with PBS. The expression level of RfCTL-S1 in the fat body of R. ferrugineus larvae at 6 h after injection of S. aureus was significantly higher than that at 24 h after injection of S. aureus. In the gut of R. ferrugineus larvae, the expression level of RfCTL-S1 at 12 h after challenge with S. aureus was significantly higher than those at 6 and 24 h after challenge with S. aureus. After RfCTL-S1 was silenced by RNAi, the expression levels of three antimicrobial peptide genes RfCecropin, RfColeoptericin and RfDefensin in the fat body of R. ferrugineus larvae were significantly reduced, and the ability of R. ferrugineus larvae to clear the invaded EGFP-tagged E. coli in the hemolymph was significantly impaired as compared to the control. However, no significant difference was determined in the number of cultivable bacterial colonies in the larval gut between the RNAi group and the control group. 【Conclusion】 Secretory RfCTL-S1 protein can mount the expression of antimicrobial peptide genes by recognizing bacteria and activating the corresponding immune signaling pathways in the fat body of R. ferrugineus larvae, thus to eliminate invaded pathogens.

Effects of low temperature on diapause termination and the expression levels of ecdysone receptor gene EcR and heat shock proteins genes Hsp70 and Hsp90 in Sitodiplosis mosellana (Diptera: Cecidomyidae)

ZHANG Guo-Jun, WANG Wen, NAN Jiang-Lei, CHENG Wei-Ning, ZHU Ke-Yan

2021, 64(12): 1398-1406. doi:10.16380/j.kcxb.2021.12.005

Abstract ( 69 )

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【Aim】 This study aims to clarify the feasibility of using the cocoon breaking rate and time required for cocoon breaking as the indicators for diapause termination of the wheat midge, Sitodiplosis mosellana, a typical insect pest with obligatory larval diapause, and to explore the potential roles of ecdysone receptor gene EcR and heat shock protein 70 and 90 genes (Hsp70 and Hsp90) during diapause termination under low temperature conditions. 【Methods】 The field-collected diapausing larvae of S. mosellanain early September were exposed to low temperature (4℃) and natural temperature, respectively, for different time (0-90 d) prior to pupation at 24℃ in the laboratory, their cocoon breaking and pupation rates and the time required for their cocoon breaking and pupation were investigated. The mRNA levels of EcR, Hsp70 and Hsp90 in cocooned larvae of S. mosellana after diapause termination stimulated by low temperature (4℃) and followed developmental resumption at 24℃ were assayed by qPCR. 【Results】 The cocoon breaking and pupation rates and the time required for cocoon breaking and pupation of S. mosellana larvae exposed to low temperature (4℃) and natural temperature for different time differed significantly. Larvae not subjected to low temperature (4℃) treatment were unable to pupate, but 71.3% of individuals were able to break cocoons when enough water was supplied. Both the cocoon breaking rate and pupation rate increased, the time required for cocoon breaking and pupation gradually shortened with the increasing of the low temperature (4℃) treatment time within 60 d. The pupation rate of S. mosellana larvae exposed to natural temperature for 30-60 d was significantly lower than that of larvae exposed to 4℃ for 30-60 d. After the larvae were exposed to low temperature (4℃) for 60 d and natural temperature for 90 d, more than 91% of individuals pupated. Low temperature treatment at 4℃ significantly increased the expression levels of EcR, Hsp70 and Hsp90 in S. mosellana larvae, and their expression levels in larvae exposed to low temperature for 30 d were the highest. The expression levels of EcR, Hsp70 and Hsp90 in S. mosellana larvae exposed to low temperature decreased gradually with the increasing of the treatment time, and became stable in most larvae after diapause termination. 【Conclusion】 Low temperature can significantly promote the diapause termination of S. mosellana. Low temperature affects diapause termination more strongly than the natural temperature of September and October. Cocoon breaking rate and the time required for cocoon breaking can reflect the diapause intensity of S. mosellana larvae to a certain extent, but are not suitable separately as indicators for diapause termination. The expression levels of EcR, Hsp70 and Hsp90 are closely related to diapause intensity, and they might play potential roles in the diapause termination of S. mosellana.

Molecular characterization of heat shock protein 70 (HSP70) genes from Pieris rapae (Lepidoptera: Pieridae) and their responses to insecticide stress

DING Chao-Yang, ZHAO Le, LIU Su, LI Mao-Ye

2021, 64(12): 1407-1416. doi:10.16380/j.kcxb.2021.12.006

Abstract ( 57 )

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【Aim】 This study aims to determine the molecular characteristics of heat shock protein 70 (HSP70) genes in the small white butterfly, Pieris rapae and their response to insecticide stress, thus to pave the way for exploring the role of HSP70s in defense against insecticides in P. rapae. 【Methods】 Homology-basedsearchmethodwasusedtoidentifyHSP70 genes from the transcriptome dataset of P. rapae. Bioinformatic programs were used to analyze the molecular characteristics of these HSP70 genes. Real-time quantitative PCR was performed to determine the expression profiles of HSP70 genes at different developmental stages (2nd-5th instar larvae, pupae, and female and male adults), in different tissues of the 4th instar larvae (midgut, Malpighian tubules, fat body and integument) of P. rapae, and in the 4th instar larvae exposed to LD₂₀ of lambda-cyhalothrin (0.12 ng/μL) and chlorantraniliprole (1.04 ng/μL). 【Results】 Three HSP70 genes (PrHsp70-1, PrHsp70-2 and PrHsp70-3 with the GenBank accession numbers of MW691114, MW691115 and MW691116, respectively) were identified from the transcriptome of P. rapae. PrHSP70 proteins encoded by PrHsp70-1, PrHsp70-2 and PrHsp70-3 consist of 628, 630 and 653 amino acid residues, respectively, and have the molecular masses of 68.7, 69.2 and 71.7 kD, respectively. The results of bioinformatic analysis indicated that all of the three PrHSP70 proteins are localized within the cytosol and have the signature motifs of HSP70 family. PrHsp70-1 and PrHsp70-2 are intronless, whereas PrHsp70-3 contains an intron. The expression levels of PrHsp70-1 and PrHsp70-2 were upregulated along with the increase of larval instars and downregulated during pupal and adult stages. By contrast, the expression levels of PrHsp70-3 in P. rapae among different developmental stages showed no significant difference. PrHsp70-1 and PrHsp70-2 were highly expressed in larval fat body and midgut, respectively, while PrHsp70-3 displayed higher transcription level in both larval integument and fat body. Treatment with LD₂₀of lambda-cyhalothrin and chlorantraniliprole caused significant upregulation of the three PrHsp70 genes, although their responses varied with time. Moreover, the transcription level of PrHsp70-3 was significantly downregulated at 24 h post exposure to LD₂₀ of lambda-cyhalothrin. 【Conclusion】 PrHsp70 genes may play essential roles in the growth and development and insecticide defense in P. rapae.

Molecular cloning and temporal-spatial expression profiling of trehalose-6-phosphate synthase gene in Spodoptera frugiperda (Lepidoptera: Noctuidae) and its response to temperature stress

LIANG Yu-Jian, ZHANG Tao, LI Cao, ZHI Jun-Rui

2021, 64(12): 1417-1426. doi:10.16380/j.kcxb.2021.12.007

Abstract ( 100 )

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【Aim】 This study aims to clone SfTPS gene from the fall armyworm, Spodoptera frugiperda, and to analyze its relative expression levels in different developmental stages, different tissues and the 5th instar larvae under different temperature stresses, so as to lay the foundation for further exploring the function of TPS in the growth and development of S. frugiperda and its anti-stress response. 【Methods】 The full-length coding region of S. frugiperda SfTPS was cloned by RT-PCR technology and analyzed by bioinformatics. The relative expression levels of SfTPS in different developmental stages (egg, 1st-6th instar larva, pupa, and adult), different tissues of the 5th instar larva (integument, midgut, and fat body), and the 5th instar larvae of S. frugiperda subjected to short-term (2, 4 and 8 h) high temperature (35℃) and low temperature (10℃) stress were detected by RT-qPCR technology. 【Results】 The cDNA sequence of TPS gene of 2 571 bp was cloned from S. frugiperda and named SfTPS (GenBank accession number: MT920672). Its open reading frame (ORF) is 2 481 bp in length, encoding 826 amino acids with two conserved domains (TPS and TPP). Homologous comparison and phylogenetic analysis showed that TPS proteins in insects are highly conservative. SfTPS has the closest relationship with TPS of S. litura, showing 99.15% amino acid sequence identity. The proportions of α-helix, β-sheet and random coil in SfTPS are 38.14%, 12.23%, and 48.55%, respectively. The tertiary structure of SfTPS is homo-dimer. The RT-qPCR results showed that SfTPS was lowly expressed in the egg and 1st-5th instar larval stages of S. frugiperda, and highly expressed in the 6th instar larval, pupal and adult stages. Moreover, the relative expression level of SfTPS changed greatly before and after the metamorphosis of S. frugiperda. The tissue distribution results showed that SfTPS had the highest expression level in the fat body of the 5th instar larvae of S. frugiperda. After the 5th instar larvae of S. frugiperda were subjected to low temperature (10℃) and high temperature (35℃) stress for 2-8 h, the relative expression levels of SfTPS were significantly higher than that of the control (25℃), being 4.43-9.34- and 2.50-6.03-fold as high as that of the control, respectively. 【Conclusion】 SfTPS gene might play important roles in the growth and development, and resisting high and low temperature stress in S. frugiperda.

Establishment of the relative susceptible baselines of Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae to commonly used insecticides

WANG Huan-Huan, LV Sheng-Lan, ZHAO Rui, LIANG Pei, ZHANG Shuai, GAO Xi-Wu, ZHANG Lei, GU Shao-Hua

2021, 64(12): 1427-1432. doi:10.16380/j.kcxb.2021.12.008

Abstract ( 73 )

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【Aim】 This study aims to establish the relative susceptible baselines of the fall armyworm, Spodoptera frugiperda, to commonly used insecticides in order to provide basic data for systematically monitoring the resistance of S. frugiperda to insecticides in China. 【Methods】 S. frugiperda individuals were collected from corn fields and bred in the laboratory without exposure to any insecticides for 5-7 generations. The susceptibility of the 3rd instar larvae of S. frugiperda to seven commonly used insecticides (emamectin benzoate, spinetoram, chlorfenapyr, indoxacarb, tetrachlorantraniliprole, lufenuron and chlorantraniliprole) belonging to six pesticide categories was determined by leaf-dip method and topical application, and that of the 2nd instar larvae of S. frugiperda to these seven insecticides was determined by diet surface overlay method. Based on the bioassay results, the relative susceptible baselines of S. frugiperda to these seven insecticides were established. 【Results】 The LC₅₀or LD₅₀values of the above seven insecticides to S. frugiperda larvae were 0.054-12.131 mg/L by leaf-dip method, 0.355-4.707 μg/g by topical application (excluding lufenuron), and 0.003-0.238 μg/cm² by diet surface overlay bioassay, respectively. 【Conclusion】 The relative susceptible baselines of S. frugiperda larvae to the commonly used insecticides have been established using three different bioassay methods, providing basic data for the resistance monitoring and chemical control of S. frugiperda in China.

Effects of cold acclimation on lipid metabolism in Monochamus alternatus (Coleoptera: Cerambycidae) larvae

CHEN Jun-Xian, ZHOU Jiao, WEI Hong-Yi, ZHAO Li-Lin

2021, 64(12): 1433-1443. doi:10.16380/j.kcxb.2021.12.009

Abstract ( 74 )

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【Aim】 In low temperature environment, insects will activate the physiological regulation mechanism in vivo to stabilize their own metabolism, and fat metabolism plays an important role in the process of resisting low temperature in insects. This study aims to explore the changes in fat metabolism in Monochamus alternatus larvae under low temperature and its influence on the cold tolerance of M. alternatus. 【Methods】 The 4th instar larvae of M. alternatus reared at the room temperature (25℃) were cultured in a constant temperature incubator at 25℃ (control) and 4℃ (cold acclimation), respectively. After 7 d, the larvae were dissected and their fat bodies were collected, the changes of lipid droplets were observed, and the fat content in the fat body was measured. The composition and content of free fatty acids were detected by gas chromatography-mass spectrometry (GC-MS), and the transcript levels of genes of key enzymes involved in fatty acid β-oxidation ［carnitine palmitoyltransferase 1 (CPT1), 4-ketoacyl-CoA thiolase (4KCT), very long chain acyl-CoA dehydrogenase (VLCAD), enoyl-CoA hydratase (ECH) and 3-hydroxyacyl-CoA dehydrogenase (3HCD-1)］ were assayed by RT-qPCR. 【Results】 After the 4th instar larvae of M. alternatus were subjected to cold acclimation (4℃) for 7 d, lipid droplets in the fat body became smaller, the lipid droplet density declined and the fat content decreased as compared to those in the control. However, the composition of fatty acids did not change. The main fatty acids in the fat body of the 4th instar larvae of both the control group and cold acclimation group were C16∶0, C16∶1, C18∶0, C18∶1 and C18∶2, of which the relative content of C18∶2 in both the two groups was the highest, decreasing from 31.83%±8.82% to 25.16%±2.88% after cold acclimation. After the 4th instar larvae of M. alternatus were subjected to cold acclimation, the relative contents of C16∶0, C16∶1 and C18∶2 in the fat body decreased, while the relative contents of C18∶0 and C18∶1 increased. Among the five main fatty acids, the relative abundance of various fatty acids in the fat body of the 4th instar larvae in the cold acclimation group was reduced compared with that in the control, of which the relative abundance of C16∶0, C16∶1 and C18∶2 decreased significantly. However, the double-bond index of free fatty acids in the fat body of the 4th instar larvae in the cold acclimation group was increased by 3.88% as compared to that in the control. The expression level of VLCAD gene in the cold acclimation group was significantly up-regulated as compared with that in the control group. 【Conclusion】 In low temperature environment, M. alternatus larvae maintain basic metabolism by consuming fat, and the degradation level of fatty acids in the fat body increased. Unsaturated fatty acids play a key role in the cold resistance of M. alternatus. Regulation of lipid metabolism is an important survival strategy for M. alternatus to cope with low temperature.

An automatic identification and counting method of Spodoptera frugiperda (Lepidoptera: Noctuidae) adults based on sex pheromone trapping and deep learning

QIU Rong-Zhou, ZHAO Jian, HE Yu-Xian, CHEN Shao-Ping, HUANG Mei-Ling, CHI Mei-Xiang, LIANG Yong, WENG Qi-Yong

2021, 64(12): 1444-1454. doi:10.16380/j.kcxb.2021.12.010

Abstract ( 72 )

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【Aim】 To explore the feasibility of deep learning in automatic recognition counting of Spodoptera frugiperda adults, and to evaluate the recognition counting precision of the model, so as to provide image recognition and counting methods for intelligent pest monitoring by machine. 【Methods】 A self-designed pest image monitoring device based on sexual attraction was used to automatically and regularly collect images of trapped S. frugiperda adults. Combined with the collection of images of S. frugiperda adults on sticky coloured cards with ship-shape trap, a dataset was constructed. The YOLOv5 deep learning object detection model was used for feature learning. The models of Yolov5s-A1, Yolov5s-A2, Yolov5s-AB and Yolov5s-ABC were obtained by model training using different image datasets, including the original images of S. frugiperda adults, S. frugiperda adult images with edge incomplete objects removed, S. frugiperda adult images with similar detection objects (S. litura adults) added, and negative samples without detection objects. The detection results of test samples under different occlusion gradients using different models were compared. Precision (P), recall (R), F1-measure, average precision (AP), and counting accuracy (CA) were used to evaluate these models. 【Results】 The recognition precision, recall and F1-measure of Yolov5s-A1 trained by the original image set reached 87.37%, 90.24% and 88.78, respectively. The model Yolov5s-A2 trained by images with edge incomplete objects removed had a recognition precision of 93.15%, a recall of 84.77%, and F1-measure of 88.76. The recognition precision, recall and F1-measure of Yolov5s-AB trained by images of added S. litura adult samples reached 96.23%, 91.85% and 93.99, respectively. The model Yolov5s-ABC trained by negative samples without detection objects had a recognition precision of 94.76%, a recall of 88.23%, and F1-measure of 91.38. The order of average precision of four models from high to low was as follows: Yolov5s-AB>Yolov5s-ABC>Yolov5s-A2>Yolov5s-A1; and the result of Yolov5s-AB was similar to that of Yolov5s-ABC. The order of counting accuracy of four models from high to low was as follows: Yolov5s-AB>Yolov5s-ABC>Yolov5s-A2>Yolov5s-A1. 【Conclusion】 The results show that the method developed in this study is applicable for the recognition and counting of S. frugiperda adults on pest image monitoring equipment and the sticky coloured card with trap under control conditions, and the deep learning technology is effective for the identification and counting of S. frugiperda adults. The automatic recognition and counting method for S. frugiperda adults based on deep learning has good robustness to insect body posture changes, sundries interference, etc. It can automatically count the number of S. frugiperda adults with various body postures and damaged body. The method has a broad application prospect in pest population monitoring.

Dim-light vision and the mechanisms of visual adaptation in nocturnal insects

YANG Xiao-Fan, LU Zi-Yun, YUAN Shi-Tao, LI Jian-Cheng, WEI Guo-Shu

2021, 64(12): 1455-1464. doi:10.16380/j.kcxb.2021.12.011

Abstract ( 82 )

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As an important part of insects, nocturnal species have evolved some sensory mechanisms adapted to their habitats. It is generally believed that nocturnal insects mainly rely on olfaction and mechanical perception to explore habitats, and the visual system has been degraded or lost. In recent years, with the application of new biological technologies such as infrared night vision, electroretinogram (ERG) and optic nerve, breakthroughs have been made in visual and ecological research of insects. Since 2002, it has been successively found that some nocturnal insects such as moths, bees and dung beetles had evolved a remarkable capacity of dimlight vision, and can see brightness, color, shape, size, contrast, polarized light and motion at night (light intensity lower than 0.3 lx) as in bright day, showing an immense potential for visually regulating behaviors in nocturnal insects. In addition, the pupil, focal length, rod and pigment particles of compound eyes of these nocturnal insects have evolved some morphological and physiological characteristics to improve the optical sensitivity and to adapt to the dim-light environment at night. Since the study of dim-light vision and the mechanisms of visual adaptation in nocturnal insects is still in its infancy with a focus on flower-visiting or fecal-feeding insects, the research of the following aspects should be streagthened: (1) the dim-light vision in major nocturnal agricultural pests; (2) the optical structure characteristics of atypical superposition compound eye and the mechanisms of its adaptation to dim-light environment; (3) the mechanisms of visual adaptation in nocturnal insects in response to dim-light environment; and (4) the development of new pest control technology based on dim-light vision in nocturnal insects.

Research progress of endosymbionts in lepidopteran insects

LIU Yuan, WANG Hao, WANG Zhi-Peng, CHEN Li-Min, WANG Ya-Ru, HOU You-Ming

2021, 64(12): 1465-1477. doi:10.16380/j.kcxb.2021.12.012

Abstract ( 101 )

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The symbiotic relationship between endosymbionts and their insect hosts is ubiquitous in nature, and they are interdependent, interacting and coevolving. In recent years, studies on insect endosymbionts mainly focus on hemipteran and dipteran insects. However, a growing number of studies show that the interaction mode and mechanism between lepidopteran insects and their endosymbionts are also attracting more and more attention. Lepidopteran insects are widely distributed and play important roles in the ecosystem as herbivores and pollinators, and most of their larvae can cause great economic losses to the agricultural and forestry production. The diversity of endosymbiont community in lepidopteran insects is relatively low, which is mainly dominated by secondary symbiont Wolbachia. A few species are also infected with Spiroplasma, Arsenophonus and Rickettsia. These endosymbionts are mainly transmitted maternally from mother to offspring, whereas their horizontal transmission may also be occurring in nature. And they play important roles in the growth and development, reproductive manipulation, environmental adaptation and genetic evolution of hosts. Nowadays, diagnostic polymerase chain reaction (PCR), high-throughput amplicon sequencing, and metagenomic sequencing are generally used to detect endosymbionts. However, there are still some difficulties in the research of endosymbionts in lepidopteran insects, including that most endosymbionts can not be cultured in vitro, and the biological functions of endosymbionts with low abundance are difficult to be determined. Considering the distribution of endosymbionts and difficulties in lepidopteran insects, it is suggested that future research should focus on secondary symbionts and their biological functions.

Feeding preference of Monochamus saltuarius (Coleoptera: Cerambycidae) adults for four host pine trees

ZHENG Ya-Nan, SHI Yong, LI Yang, FAN Li-Chun, WANG Jue, WANG Wei-Tao

2021, 64(12): 1478-1482. doi:10.16380/j.kcxb.2021.12.013

Abstract ( 55 )

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【Aim】 Since pine wilt disease spreads to the middle temperate zone of China, Monochamus saltuarius has become a new vector of pine wood nematode in northern China. Due to the abundant pine tree species damaged by the pine wood nematode in the middle temperate zone, the preferences of M. saltuarius to four host pine trees in the process of supplementary nutrition were assessed in this study, in order to provide theoretical basis for the prevention and control of M. saltuarius and the monitoring of pine wilt disease in the middle temperate zone. 【Methods】 Before the flight period of M. saltuarius on May, 2020, Pinus koraiensis trees infected by M. saltuarius were collected from Dahuofang Experimental Forest Farm in Fushun City, Liaoning Province. The infested trees were sawed into 1 m long logs, sealed with wax at both ends, and kept in insect cages. The newly emerged adults were collected every day. Three-year-old seedlings of host plants P. koraiensis, P. tabulaeformis, P. sylvestris var. mongolica and Larix olgensis were put into the four corners of the cage, respectively. Five male and five female adults emerged on the same day were placed in the center of the cage, and the daily feeding frequency on different host pine trees and average daily feeding amount on different parts of host pine trees were investigated. 【Results】 In the cage, M. saltuarius mainly stayed on P. tabulaeformis, with the daily feeding frequency of 7.05±3.87, followed by on P. koraiensis and L. olgensis. The daily feeding frequency of staying on P. sylvestris var. mongolica was the least (1.02±0.81). The daily feeding frequencies on different species of host pine trees were significantly different between male and female adults. The feeding amounts of M. saltuarius adults on four species of pine trees were significantly different. The daily feeding amount of M. saltuarius adults on P. tabulaeformis was the highest (129.14±50.23 mm²), accounting for 62.89% of the total feeding amount, followed by those on P. koraiensis and L. olgensis. And that on P. sylvestris var. mongolica was the least (9.87±11.02 mm²), accounting for only 4.81% of the total feeding amount. The feeding amounts on different parts of the same pine tree were significantly different, and M. saltuarius adults mainly fed on the tender branches of four species of pine trees.【Conclusion】 Based on the analysis of the feeding frequency and feeding amount of M. saltuarius on different pine tree species during the period of supplementary nutrition, the preference of M. saltuarius to P. tabulaeformis is significantly higher than to the other three pine trees.

Contents of Vol. 64 Issue 12

2021, 64(12): 1483-1483.

Abstract ( 29 )

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General Contents of Volume 64(1-12)

2021, 64(12): 1484-1484.

Abstract ( 28 )

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