4th Instar Nymphs Research Articles

Structural Derivatives of β-Asarone from Acorus calamus Linn. as Insecticide Candidates and the Insecticidal Mechanism Against Small Brown Planthopper

The small brown planthopper (SBPH), Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae), is an increasing threat to Gramineae crops, posing significant risks to both the environment and food safety. β-asarone, as a promising green alternative to chemical insecticides, possesses wide application prospects in the crop protection field. To enhance the insecticidal activity of β-asarone, a series of derivatives were prepared through an active substructure splicing strategy, and their insecticidal activities against SBPH were evaluated. Among the 7 commercial compounds with chemical structures similar to β-asarone and 12 structural derivatives of β-asarone, compound 10, which incorporates the 2-chloropyridine functional group from flupyrimin, exhibited the most potent insecticidal activity against SBPH, with an 8.31-fold increase in insecticidal activity compared to β-asarone. Furthermore, transcriptome analysis showed that among the selected genes that may play important roles in insecticidal activity, an ABC transporter gene, MDR49, was most significantly down-regulated. MDR49 was highly expressed in the 4th-instar nymphs, with the highest expression level in the fat body, midgut, and abdomen. RNA interference (RNAi) against MDR49 significantly reduced susceptibility to compound 10 in SBPH, which revealed that MDR49 may be the candidate insecticidal target of compound 10. Additionally, the insecticidal spectrum revealed that compound 10 showed excellent efficacy against Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) and Tetranychus cinnabarinus (Boisduval) (Acarina: Tetranychidae). This study indicates that compound 10 could be further developed as a novel eco-friendly pesticide.

Targeting Syntaxin1A via RNA interference inhibits feeding and midgut development in Locusta migratoria.

Syntaxin1A (Syx1A) has diverse and indispensable functions in animals. Previous studies have mainly focused on the roles of Syx1A in Drosophila, and so how Syx1A operates during the development of other insects remains poorly understood. This study investigated whether disrupting LmSyx1A using RNA interference (RNAi) affects the growth and development of Locusta migratoria. LmSyx1A was expressed in all tissues tested, with the highest expression observed in the fat body. After 5th-instar nymphs were injected with double-stranded LmSyx1A (dsLmSyx1A), none of the nymphs were able to molt normally and all eventually died. The silencing of LmSyx1A resulted in the cessation of feeding, body weight loss, and atrophy of the midgut and gastric cecum in locusts. Hematoxylin and eosin (H&E) staining showed that the columnar cells in the midgut were severely damaged, with microvilli defects visible in dsLmSyx1A-injected nymphs. Secretory vesicles were observed with transmission electron microscopy (TEM). In addition, reverse transcription quantitative polymerase chain reaction (RT-qPCR) further indicates that silencing LmSyx1A repressed the expression of genes involved in the insulin/mammalian target of rapamycin (mTOR)-associated nutritional pathway. Taken together, these results suggest that LmSyx1A significantly affects the midgut cell layer of locust nymphs, which was partially associated with the downregulation of the insulin/mTOR-associated nutritional pathway. Thus, we argue that LmSyx1A is a suitable target for developing dsRNA-based biological pesticides for managing L.migratoria.

Sgabd-2 plays specific role in immune response against biopesticide Metarhizium anisopliae in Aphis citricola

Metarhizium anisopliae is an effective biopesticide for controlling Aphis citricola, which has developed resistance to many chemical pesticides. However, the powerful immune system of A. citricola has limited the insecticidal efficacy of M. anisopliae. The co-evolution between insects and entomogenous fungi has led to emergence of new antifungal immune genes, which remain incompletely understood. In this study, an important immune gene Sgabd-2 was identified from A. citricola through transcriptome analysis. Sgabd-2 gene showed high expression in the 4th instar nymph and adult stages, and was mainly distributed in the abdominal region of A. citricola. The recombinant protein (rSgabd-2) exhibited no antifungal activity but demonstrated clear agglutination activity towards the conidia of M. anisopliae. RNA interference of Sgabd-2 by dsRNA feeding resulted in decreased phenoloxidase (PO) activity and weakened defense for A. citricola against M. anisopliae. Simultaneous silence of GNBP-1 and Sgabd-2 effectively reduced the immunity of A. citricola against M. anisopliae more than the individual RNAi of GNBP-1 or Sgabd-2. Furthermore, a genetically engineered M. anisopliae expressing double-stranded RNA (dsSgabd-2) targeting Sgabd-2 in A. citricola successfully suppressed the expression of Sgabd-2 and demonstrated increased virulence against A. citricola. Our findings elucidated Sgabd-2 as a critical new antifungal immune gene and proposed a genetic engineering strategy to enhance the insecticidal virulence of entomogenous fungi through RNAi-mediated inhibition of pest immune genes.

Predator-Prey Interaction Between Xylocoris sordidus (Hemiptera: Anthocoridae) and Enneothrips enigmaticus (Thysanoptera: Thripidae).

The peanut thrips, Enneothrips enigmaticus (Thysanoptera: Thrypidae), is an important pest of the peanut (Arachis hypogaea) in South America. Due to concerns about the environment and human health induced by the extensive use of pesticides in the management control of pests, environmentally and friendlier tactics must be targeted. Thus, this study investigates, for the first time, the behavior of Xylocoris sordidus (Hemiptera: Anthocoridae) as a biological control agent for E. enigmaticus. The methodology included no-choice tests to assess whether the predation rate varies according to the developmental stage of the prey, as well as the predator's developmental stage with the highest predation capacity. Additionally, an analysis of the functional response of adult and 5th instar nymphs of X. sordidus exposed to different densities of E. enigmaticus nymphs (1, 2, 4, 8, 16, and 32) was conducted. The results confirm the predation of peanut thrips by X. sordidus, with a higher predation rate in the nymphal stages of the prey. There was no difference in predation capacity between predator nymphs and adults, and exhibiting a type II functional response. Therefore, the potential of X. sordidus as a biological control agent for E. enigmaticus is confirmed, showing the importance of adopting measures to preserve this predator in peanut crops.

Identification of amino acid residues that are crucial for afidopyropen binding to the TRPV channel of Myzus persicae (Sulzer)

Afidopyropen is highly effective against sucking insects, including the Myzus persicae, that modulates the transient receptor potential vanilloid (TRPV) channel. However, the action mechanisms of afidopyropen to the TRPV channel remain unknown. In this study, the genes encoding the Nanchung (MpNan) and Inactive (MpIav) subunits of the TRPV channel of M. persicae (MpTRPV) were cloned, and their spatiotemporal expression profiles were investigated. Then, MpTRPV was functionally expressed in Xenopus laevis oocytes, and the AA residues crucial for afidopyropen binding were identified using the two-electrode voltage clamp (TEVC) technique. The results showed that both MpNan and MpIav exhibited the highest expression in the antennae and were most abundant in the 4th instar nymphs and adults. Knockdown of these two genes by RNAi greatly increased the toxicity of afidopyropen to the aphids. Moreover, the AA residues involved in afidopyropen binding to MpNan were predicted and L412 was further identified as the key residue for binding by TEVC analysis. The results also showed that afdopyropen and pymetrozine share the same binding site. These findings lay a foundation not only for exploring the mechanisms of pest target resistance to afidopyropen and pymetrozine but also for developing new insecticides targeting the TRPV channels of pests.

Wing expansion functional analysis of ion transport peptide gene in Sogatella furcifera (Horváth) (Hemiptera: Delphacidae)

Ion transport peptide (ITP), a superfamily of arthropod neuropeptides, serves a crucial role in regulating various physiological processes such as diuresis, ecdysis behavior, and wing expansion. However, the molecular characteristics, expression profile, and role of ITP in Sogatella furcifera are poorly understood. To elucidate the characteristics and biological function of ITP in S. furcifera, we employed reverse transcription-polymerase chain reaction (RT-PCR) and RNA interference (RNAi) methods. The identified SfITP gene encodes 117 amino acids. The expression of SfITP gradually increased followed the formation of 3-day-old of 5th instar nymph, peaking initially at 40 min after eclosion, and reaching another peak 24 h after eclosion, with particularly high expression levels in thorax and wing tissues. Notably, SfITP RNAi in 3rd instar nymphs of S. furcifera significantly inhibited the transcript levels of SfITP, resulting in 55% mortality and 78% wing deformity. These findings suggests that SfITP is involved in the regulation of wing expansion in S. furcifera, providing insights into the regulation of insect wing expansion and contributing to the molecular understanding of this process.

Parasitoid-host interaction behaviors in relation to host stages in the Tamarixia triozae (Hymenoptera: Eulophidae)-Bactericera cockerelli (Hemiptera: Triozidae) system.

Females of host-feeding parasitic wasps often partition hosts of different stages for feeding and parasitization, but the underlying behavioral mechanisms are largely unknown, making it difficult to evaluate parasitoid-host interactions and their effects on biological control success. Tamarixia triozae (Burks) is an ectoparasitoid of tomato-potato psyllid Bactericera cockerelli (Šulc), which utilizes nymphs and kills them both by parasitization and host feeding. In this study, we exposed female wasps to 1st- to 5th-instar psyllid nymphs simultaneously and made 13-h continuous video recording of parasitoid-host interactions. We then quantified host stage-dependent handling time for feeding and oviposition and behaviors of parasitoid attacks and host defenses from encountering to successful feeding and oviposition. Female wasps were more likely to encounter and evaluate older hosts. However, the encounter and evaluation did not necessarily result in the success of feeding and oviposition. Our findings suggest that (i) T. triozae continues to assess the host using its ovipositor after the evaluation phase, (ii) females prefer the mid-aged hosts for feeding piercing and feeding and the later instars for oviposition probing and oviposition, (iii) the combination of stage-specific host nutrition value, integument thickness and defense behavior determines the success of feeding attacks, and (iv) the optimal host resource for parasitoid offspring fitness defines host stage selection for oviposition. This study contributes to our understanding of parasitoid-host interactions and mechanisms behind host stage selections.

The synergistic regulatory effect of PTP1B and PTK inhibitors on the development of Oedaleus decorus asiaticus Bei-Bienko

Tyrosine phosphorylation is crucial for controlling normal cell growth, survival, intercellular communication, gene transcription, immune responses, and other processes. protein tyrosine phosphatase (PTP) and protein tyrosine kinases (PTK) can achieve this goal by regulating multiple signaling pathways. Oedaleus decorus asiaticus is an important pest that infests the Mongolian Plateau grassland. We aimed to evaluate the survival rate, growth rate, overall performance, and ovarian developmental morphology of the 4th instar nymphs of O. decorus asiaticus while inhibiting the activity of protein tyrosine phosphatase-1B (PTP1B) and PTK. In addition, the expression and protein phosphorylation levels of key genes in the MAPK signaling pathway and antioxidant enzyme activity were assessed. The results showed no significant differences in survival rate, growth rate, or overall performance between PTP1B inhibitor treatment and control. However, after PTK inhibitor treatment, these indexes were significantly lower than those in the control. The ovarian size of female larvae after 15 days of treatment with PTK inhibitors showed significantly slower development, while female larvae treated with PTP1B exhibited faster ovarian growth than the control group. In comparison to controls and nymphs treated with PTK inhibitors, the expression and phosphorylation levels of key genes in the MAPK signaling pathway under PTP1B inhibitor treatments were significantly higher in 4th instar nymphs. However, reactiveoxygen (ROS) species levels and the activities of NADPH oxidase and other antioxidant enzymes were considerably reduced, although they were significantly greater in the PTK inhibitor treatment. The results suggest that PTP1B and PTK feedback inhibition in the mitogen-activated-protein kinases (MAPK) signal transfer can regulate the physiological metabolism of the insect as well as its developmental rate. These findings can facilitate future uses of PTP1B and PTK inhibitors in controlling insect development to help control pest populations.

Inhibition of ecdysone receptor (DcEcR) and ultraspiracle (DcUSP) expression in Diaphorina citri increased susceptibility to pesticides

Diaphorina citri Kuwayama is of great concern because of its ability to transmit devastating citrus greening illness (Huanglongbing). One strategy for controlling HLB may involve limiting the spread of D. citri. Insecticides using dsRNA target genes may be a useful option to control D. citri. The ecdysone receptor (EcR) and ultraspiracle (USP) are crucial for the growth and reproduction of insects. This study identified the genes for D. citri ecdysone receptor (DcEcR) and ultraspiracle (DcUSP). According to the qPCR data, DcUSP peaked at the 5th-instar nymph stage, while DcEcR peaked at the adult stage. Females expressed DcEcR and DcUSP at much higher levels than males. RNAi was used to examine DcEcR and DcUSP function. The findings demonstrated that inhibition of DcEcR and DcUSP delayed nymph development and decreased survival and eclosion rates. dsEcR caused adults to develop deformed wings, and dsUSP caused nymphs to wither and die. Female adult ovaries developed slowly, and the females laid fewer eggs. Additionally, DcEcR and DcUSP were inhibited, increasing D. citri susceptibility to pesticides. These findings suggest that DcEcR and DcUSP are critical for D. citri development, growth, and reproduction and may serve as potential targets for D. citri management.

Effects of different host plants on population fitness of pea aphid (Acyrthosiphon pisum)

BackgroundHost plants not only provide and living places and energy materials for insects, but also influence insect population parameters and population fitness. MethodsThis study examined the influence of various host plant species on the fitness of pea aphid (Acyrthosiphon pisum). The biological parameters and population parameters of pea aphid on 6 different host plants (Vicia fabae, Pisum sativum, Medicago sativa, Trifolium pratense, Onobrychis viciaefolia and Melilotus officinalis) were observed and counted by ecological experiments, which were carried out in a control chamber. ResultsThe results showed that the developmental duration of 1st and 2nd instar nymphs of pea aphids on T. pratense and P. sativum was significantly prolonged, whereas that of 3rd and 4th instar nymphs on O. viciaefolia and M. officinalis was significantly shortened. Compared with the pea aphid on the V. faba, the longevity of adults on M. officinalis and P. sativum was significantly prolonged, but only the generation time on P. sativum was significantly prolonged. Moreover, the survival rate of nymphs was significantly lower on O. viciaefolia and M. sativa than on others. Net reproductive rate and mean generation time on V. faba were significantly higher than in other host plants. The intrinsic rate of increase (rm) and finite rate of increase (λ) of pea aphid feeding of A. pisum on P. sativum and O. viciaefolia decreased. However, those on the double population time on P. sativum and O. viciaefolia were significantly higher than the others. ConclusionThe findings will clarify the population fitness of pea aphids on different hosts and guide the rational distribution of different host plants, and provide new references for aphid control strategies.

A microRNA, PC-5p-30_205949, regulates triflumezopyrim susceptibility in Laodelphax striatellus (Fallén) by targeting CYP419A1 and ABCG23

MicroRNAs (miRNAs) are known to be important post-transcriptional regulators of gene expression and have been shown to be associated with insecticide resistance in insects. In this research, we show that a miRNA, PC-5p-30_205949, is involved in triflumezopyrim susceptibility via regulating expressive abundance of cytochrome P450 CYP419A1 and ATP-binding cassette transporters ABCG23 in the small brown planthopper (SBPH), Laodelphax striatellus (Fallén). Triflumezopyrim treatment significantly reduced the abundance of PC-5p-30_205949, feeding of agomir-PC-5p-30_205949 significantly increased the sensitivity of SBPH to triflumezopyrim, and its spatiotemporal expression profiles showed that PC-5p-30_205949 were expressed at all developmental stages and were highly expressed in head tissue. By software prediction and dual luciferase reporter assay, the target genes of PC-5p-30_205949 were identified as two detoxification metabolism genes CYP419A1 and ABCG23. The relative expressions of CYP419A1 and ABCG23 were significantly up-regulated after 24 h, 48 h and 72 h with triflumezopyrim exposure. CYP419A1 was highly expressed in the 4th-instar nymphs and male adults, with the highest expression level in fat body. ABCG23 was highly expressed in female adults, and had the highest expression in head. Furthermore, silencing of CYP419A1 and ABCG23 by RNA interference significantly increased the mortality of SBPH to triflumezopyrim, and molecular docking showed that CYP419A1 and ABCG23 could stably bind to triflumezopyrim with binding free energies of −171.5622 and − 103.3402 kcal mol−1, respectively. These results suggest that SBPH has a strategy to enhance the resistance to triflumezopyrim by attenuating the expression of PC-5P-30_205949, thereby activating the detoxification metabolic pathway by targeting CYP419A1 and ABCG23.

Interaction Analysis of lncRNA and mRNA Based on the Full-Length Transcriptome of the Nymph-to-Adult Developmental Transition of Sogatella furcifera

Little is known on how long noncoding RNAs (lncRNAs) and mRNAs cooperatively participate in regulating the nymph-to-adult development transition of Sogatella furcifera. Herein, lncRNA and mRNA libraries were constructed in three different developmental stages of S. furcifera, namely, prior to (PE), during (DE), and after (AE) ecdysis. Overall, 4649 lncRNAs were identified and divided into intergenic (53.90%), intronic (1.33%), sense (8.99%), antisense (21.75%), and bidirectional (3.94%) lncRNAs. Moreover, 795 differentially expressed lncRNAs were identified. Specifically, upon comparing PE and DE, 2719 target mRNAs were predicted for 574 lncRNAs. Upon comparing PE and AE, 2816 target mRNAs were predicted for 627 lncRNAs. Finally, upon comparing DE and AE, 51 target mRNAs were predicted for 35 lncRNAs. Kyoto Encyclopedia of Genes and Genome functional enrichment analysis revealed that the target genes of 795 lncRNAs were enriched in metabolic pathways, amino sugar and nucleotide sugar metabolism, and fatty acid metabolism. Subsequently, interaction analysis indicated that MSTRG.16086.1, MSTRG.16087.1, and MSTRG.2447.1 were functionally associated with cuticle protein and chitin biosynthesis. Finally, 11 differentially expressed lncRNAs were significantly enriched in 3rd and 4th instar nymphs. Our findings suggest that lncRNAs play a critical regulatory role during the molting of S. furcifera.

Changes in life history parameters and transcriptome profile of Serangium japonicum associated with feeding on natural prey (Bemisia tabaci) and alternate host (Corcyra cephalonica eggs)

BackgroundThe mass production of natural predators with prolonged shelf life is a prerequisite for their field application as pest control agents. The traditional methods used for the mass production of Serangium japonicum rely heavily on the consistent supply of natural prey. This study explains the effects of B. tabaci (natural prey) and C. cephalonica eggs (alternative food) on life history and transcriptome profile of S. japanicum.MethodsThis study compares the effects of B. tabaci (natural prey) and C. cephalonica eggs (alternative food) on biology, reproduction, and predatory efficacy, and transcriptome profile of S. japanicum.ResultsThis study revealed that S. japonicum was able to successfully complete its life cycle while feeding on B. tabaci (natural prey) and C. cephalonica eggs (alternative food). The C. cephalonica eggs fed S. japonicum individuals had longer developmental period and lower fecundity as compared to those feeding on whitefly but the survival rates (3rd instar nymphs, 4th instar nymphs and pupae) and predatory efficacy of C. cephalonica eggs fed S. japonicum individuals were significantly similar to to those feeding on whitefly.Transcriptome analysis showed that when faced with dietary changes, S. japanicum could successfully feed on C. cephalonica eggs by regulating genes related to nutrient transport, metabolism, and detoxification. Moreover, S. japanicum degraded excess cellular components through ribosomal autophagy and apoptosis, which provided sufficient materials and energy for survival and basic metabolism.ConclusionCorcyra cephalonica eggs can be used as an alternate host for the predator, Serangium japonicum, as the survival rates and predatory efficacy of the predator are similar to those feeding on the natural host (B.tabaci). When faced with dietary changes, S. japanicum could successfully feed on C. cephalonica eggs as revealed by upregulation of genes related to nutrient transport, metabolism, and detoxification. These findings are of great significance for studying the functional evolution of S. japonicum in response to dietary changes.

The phylogeny and distribution of Wolbachia in two pathogen vector insects, Asian citrus psyllid and Longan psyllid.

Wolbachia is the most abundant bacterial endosymbiont among insects. It can play a prominent role in the development, reproduction and immunity of its given insect host. To date, Wolbachia presence is well studied within aphids, whiteflies and planthoppers, but relatively few studies have investigated its presence in psyllids. Here, the infection status of Wolbachia in five species of psyllid, including Asian citrus psyllid Diaphorina citri and longan psyllid Cornegenapsylla sinica was investigated. The phylogenetic relationships of different Wolbachia lines and their infection density and patterns in D. citri and C. sinica from different countries was also examined. The infection rates of Wolbachia in D. citri and C. sinica were both 100%, and their sequencing types are ST173 and ST532 respectively. Phylogenetic analysis revealed that the Wolbachia lines in D. citri and C. sinica both belong to the Con subgroup of Wolbachia supergroup B. In addition, Wolbachia displayed a scattered localization pattern in the 5th instar nymphs and in the reproductive organs of both D. citri and C. sinica but differed in other tissues; it was highest in the midgut, lowest in the salivary glands and medium in both the testes and ovaries. Our findings assist in further understanding the coevolution of Wolbachia and its psyllid hosts. Given that Wolbachia could play an important role in insect pest control and pathogen transmission inhibition, our findings may also provide new insights for development of control strategies for D. citri and C. sinica.

Sublethal Effects of Beauveria bassiana Strain BEdy1 on the Development and Reproduction of the White-Backed Planthopper, Sogatella furcifera (Horváth) (Hemiptera: Delphacidae).

Rice (Oryza sativa) is the most important food crop all over the world, while white-backed planthopper (WBPH), Sogatella furcifera (Horváth) (Hemiptera: Delphacidae) is an important pest causing rice yield reduction. The purpose of this study is to evaluate the sublethal effects of strain BEdy1 Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Cordycipitaceae) on S. furcifera using the two-sex life table analytical method, compare the life tables of the F0 and F1 generations of WBPHs which were treated with sublethal concentrations (LC10, LC25) of B. bassiana BEdy1 with a control group. The results showed that the duration of the egg, 4th-instar and 5th-instar nymph, pre-adult, total pre-oviposition (TPOP) and mean generation time (T) for the LC25 treatment were significantly longer than those of the control and LC10 treatment. However, the duration of the adult, the longevity of male and female adults and the oviposition days of female adults for the LC25 treatment were significantly shortened. The fecundity of female adults, intrinsic rate of increase (r), net reproductive rate (R0) and finite rate of increase (λ) for the LC25 treatment were significantly decreased compared with those of other treatments. The duration of the egg and pre-adult stage for the LC10 treatment were longer than those of the control group, but the population parameters showed no significant difference. Therefore, the LC25 of B. bassiana BEdy1 can inhibit the population growth of S. furcifera.

Insect Growth Disruptors Cause Mouthpart Malformations, Inhibition of Feeding, and Mortality in the Neotropical Brown Stink Bug Euschistus heros (Hemiptera: Pentatomidae)

The Neotropical brown stink bug, Euschistus heros, is the most important sucking pest of soybean crops, quantitatively and qualitatively affecting grain and seed. This study aimed to determine mouthpart deformities, feeding inhibition, and E. heros nymphs’ mortality when in contact with insect growth disruptors (IGDs). The effects of two insecticides of the chitin biosynthesis inhibitor group (CBIs), lufenuron and diflubenzuron, and the juvenile hormone analog pyriproxyfen were tested in the laboratory. CBI application promoted mouthpart deformities, feeding inhibition, alteration of metamorphosis, and mortality of E. heros nymphs. Although pyriproxyfen did not cause mouthpart deformation, it caused certain mortality for nymphs, possibly due to physiological disorders. Lufenuron caused feed inhibition and mortality in less time when compared with diflubenzuron and pyriproxyfen. It was also more toxic to 4th instar nymphs. The insecticides, when used in higher concentrations, increased nymph’s mortality in less time. Nymphs with deformed mouthparts were unable to feed and died. All IGDs in the tested concentrations caused 100% mortality and prevented adult formation.

A Non-Gradual Development Process of Cicada Eyes at the End of the Fifth-Instar Nymphal Stage to Obtain Visual Ability.

Insects' visual system is directly related to ecology and critical for their survival. Some cicadas present obvious differences in color and ultrastructure of compound eyes between nymphal and adult stages, but little is known about when cicadas obtain their visual ability to deal with the novel above-ground habitat. We use transcriptome analyses and reveal that cicada Meimuna mongolica has a trichromatic color vision system and that the eyes undergo a non-gradual development process at the end of the 5th-instar nymphal stage. The white-eye 5th-instar nymphs (i.e., younger 5th-instar nymphs) have no visual ability because critical components of the visual system are deficient. The transformation of eyes toward possessing visual function takes place after a tipping point in the transition phase from the white-eye period to the subsequent red-eye period, which is related to a decrease of Juvenile Hormone. The period shortly after adult emergence is also critical for eye development. Key differentially-expressed genes related to phototransduction and chromophore synthesis play positive roles for cicadas to adapt to above-ground habitat. The accumulation of ommochromes corresponds to the color change of eyes from white to red and dark brown during the end of the 5th-instar nymphal period. Cuticle tanning leads to eye color changing from dark-brown to light-brown during the early adult stage. We hypothesize that the accumulation of ommochromes occurring at the end of 5th-instar nymphal stage and the early adult stage is not only for cicadas to obtain visual ability, but also is a secure strategy to cope with potential photodamage after emergence.

First record of three alien Auchenorrhyncha species from Europe: Acanalonia bivittata (Say, 1825), Branchana xanthota Li, 2011, and Dryadomorpha pallida Kirkaldy 1906 (Hemiptera: Auchenorrhyncha: Acanaloniidae, Cicadellidae)

Three alien Auchenorrhyncha species are recorded for the first time from Europe (northern Italy): the Nearctic planthopper Acanalonia bivittata (Say, 1825), the Asian leafhopper Branchana xanthota Li, 2011, and the leafhopper Dryadomorpha pallida Kirkaldy 1906, present in the Afrotropical, Palearctic, Oriental and Australian regions. Observations on morphology and data on biology and host plants are provided. The 5th instar nymph of Dryadomorpha pallida is described. Considerations and data about the increase of alien Auchenorrhyncha species in Europe are discussed.

SPARC plays an important role in the oviposition and nymphal development in Nilaparvata lugens Stål

BackgroundThe brown planthopper (Nilaparvata lugens Stål)is a notorious rice pest in many areas of Asia. Study on the molecular mechanisms underlying its development and reproduction will provide scientific basis for effective control. SPARC (Secreted Protein, Acidic and Rich in Cysteine) is one of structural component of the extracellular matrix, which influences a diverse array of biological functions. In this study, the gene for SPARC was identified and functionally analysed from N.lugens.ResultsThe result showed that the NlSPARC mRNA was highly expressed in fat body, hemolymph and early embryo. The mortality increased significantly when NlSPARC was downregulated after RNA interference (RNAi) in 3 ~ 4th instar nymphs. Downregulation of NlSPARC in adults significantly reduced the number of eggs and offspring, as well as the transcription level of NlSPARC in newly hatched nymphs and survival rate in progeny. The observation with microanatomy on individuals after NlSPARC RNAi showed smaller and less abundant fat body than that in control. No obvious morphological abnormalities in the nymphal development and no differences in development of internal reproductive organ were observed when compared with control.ConclusionNlSPARC is required for oviposition and nymphal development mainly through regulating the tissue of fat body in N.lugens. NlSPARC could be a new candidate target for controlling the rapid propagation of N.lugens population. Our results also demonstrated that the effect of NlSPARC RNAi can transfer to the next generation in N.lugens.

Isolation and screening of entomopathogenic fungi against the grasshopper Oxya chinensis (Orthoptera: Acrididae) from rice fields in Thua Thien Hue, Vietnam

Abstract. Cuong LCV, Souvannalath B, Ha TP, Lien LQ, Tam VTT, Hoai PTT, Anh HLT, Dat TTH. 2022. Isolation and screening of entomopathogenic fungi against the grasshopper Oxya chinensis (Orthoptera: Acrididae) from rice fields in Thua Thien Hue, Vietnam. Biodiversitas 23: 4906-4911. The grasshopper Oxya chinensis is one of the most abundant herbivorous insects of rice plants in Vietnam and causes severe damage to the crop. Therefore, biological control has become a particularly valuable method for grasshopper and insect control in agricultural production. The aim of the present study was to isolate and investigate the potential entomopathogenic fungi against the grasshopper O. chinensis from rice fields in Thua Thien Hue, to develop environmentally friendly bio-insecticides. The results showed that 37 fungal isolates were isolated from dead grasshoppers collected from rice fields in Thua Thien Hue province. Results of pathogenicity screening of 12 selected fungal isolates showed that the mortality rate of 4th-instar grasshopper nymphs O. chinensis ranged from 21.99% to 100% after 15 treatment days at a concentration of 1 × 108 conidia/ml. Of these, three fungal isolates, namely NL3, NL4, NL12 showed the highest pathogenicity against the grasshopper O. chinensis with mortality rates of 87.73%, 89.81%, and 100%, respectively after 15 days. LC50 values of NL3, NL4, NL12 isolates against 4th-instar nymphs and adults of O. chinensis ranged from 9.5×104 to 4.8×105 conidia/mL and 7.8 × 106 to 2.5 × 106 conidia/mL, respectively at 7 days. LT50 values of NL3, NL4, NL12 isolates against 4th-instar nymphs and adults of O. chinensis were from 4.1 to 4.9 days and 5.5 to 6.1 days, respectively at a concentration of 1 × 108 conidia/mL. Results from morphological identification and nuclear ribosomal internal transcribed spacer (ITS) gene sequence showed that three potential entomopathogenic fungi were Aspergillus tamarii, Beauveria bassiana, and Metarhizium anisopliae. The pathogenicity of Aspergillus tamarii, Beauveria bassiana, and Metarhizium anisopliae against the grasshopper O. chinensis is reported for the first time. The present investigation revealed that these entomopathogenic fungi could be a useful source for developing environment-friendly bio-insecticides for sustainable agricultural production.