Bulletin of Entomological Research最新文献

Calling males of Anastrepha obliqua release volatile compounds to attract conspecific males to form leks and females to mate. Male volatiles from Mexican and Brazilian populations of A. obliqua have been previously identified. However, there are differences in the number and identity of volatile compounds between the populations. These differences in volatile profiles may be due to male origin (e.g. wild or mass-reared flies) or methodological issues (e.g. sampling techniques). In this study, we evaluated the attractiveness of wild, laboratory non-irradiated, and laboratory-irradiated flies under semi-field conditions. Male volatiles were collected using dynamic headspace sampling (DHS) and solid-phase microextraction (SPME) techniques, and identified using gas chromatography-coupled mass spectrometry. The results showed no difference in the attractiveness of wild, laboratory non-irradiated, and irradiated males to females. However, the number of captured females differed according to the origin; wild and non-irradiated females were captured more frequently than the irradiated flies. A total of 21 compounds were found using SPME, whereas only 12 were collected using DHS, although the relative amounts of these compounds were higher than those obtained using the former sampling technique. In addition, only laboratory non-irradiated males released α-pinene and menthol, which have not been previously reported in this fruit fly species. Additionally, we identified novel compounds in A. obliqua; however, certain compounds previously reported were not detected. This study suggests that despite the qualitative and quantitative variations in the volatile profiles of A. obliqua males, their attractiveness was unaffected.

Peach-potato aphids, Myzus persicae Sulzer (Hemiptera:Aphididae), and cabbage aphids, Brevicoryne brassicae Linnaeus (Hemiptera:Aphididae), are herbivorous insects of significant agricultural importance. Aphids can harbour a range of non-essential (facultative) endosymbiotic bacteria that confer multiple costs and benefits to the host aphid. A key endosymbiont-derived phenotype is protection against parasitoid wasps, and this protective phenotype has been associated with several defensive enodsymbionts. In recent years greater emphasis has been placed on developing alternative pest management strategies, including the increased use of natural enemies such as parasitoids wasps. For the success of aphid control strategies to be estimated the presence of defensive endosymbionts that can potentially disrupt the success of biocontrol agents needs to be determined in natural aphid populations. Here, we sampled aphids and mummies (parasitised aphids) from an important rapeseed production region in Germany and used multiplex PCR assays to characterise the endosymbiont communities. We found that aphids rarely harboured facultative endosymbionts, with 3.6% of M. persicae and 0% of B. brassicae populations forming facultative endosymbiont associations. This is comparable with endosymbiont prevalence described for M. persicae populations surveyed in Australia, Europe, Chile, and USA where endosymbiont infection frequencies range form 0-2%, but is in contrast with observations from China where M. persicae populations have more abundant and diverse endosymbiotic communities (endosymbionts present in over 50% of aphid populations).

Puparia are commonly found in tsetse fly larviposition sites during studies on larval ecology. This chitinous shell is representative of past or ongoing exploitation of these sites by tsetse flies. The morphological characteristics of the puparium are not sufficiently distinctive to allow identification of the species. This study explores the applicability of biomolecular techniques on empty puparia for tsetse fly species identification. Five techniques were compared for DNA extraction from tsetse fly puparia, 1/Chelex^® 100 Resin, 2/CTAB, 3/Livak's protocol, 4/DEB + proteinase K and 5/QIAamp^® DNA Mini kit, using two homogenisation methods (manual and automated). Using a combination of two primer pairs, Chelex, CTAB, and DEB + K proved the most efficient on fresh puparia with 90, 85, and 70% samples identified, respectively. Shifting from fresh to one- to nine-month-old puparia, the Chelex method gave the best result allowing species identification on puparia up to seven months old. The subsequent testing of the Chelex extraction protocol identified 152 (60%) of 252 field-collected puparia samples at species level. The results show that reliable genetic identification of tsetse flies species can be performed from empty puparia, what can prove of great interest for future ecological studies on larviposition sites. The Chelex technique was the most efficient for DNA extraction, though the age-limit of the samples stood at seven months, beyond which DNA degradation probably compromises the genetic analysis.

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is the key vector insect transmitting the Candidatus Liberibacter asiaticus (CLas) bacterium that causes the devastating citrus greening disease (Huanglongbing, HLB) worldwide. The D. citri salivary glands (SG) exhibit an important barrier against the transmission of HLB pathogen. However, knowledge on the molecular mechanism of SG defence against CLas infection is still limited. In the present study, we compared the SG transcriptomic response of CLas-free and CLas-infected D. citri using an illumine paired-end RNA sequencing. In total of 861 differentially expressed genes (DEGs) in the SG upon CLas infection, including 202 upregulated DEGs and 659 downregulated DEGs were identified. Functional annotation analysis showed that most of the DEGs were associated with cellular processes, metabolic processes, and the immune response. Gene ontology and Kyoto Encyclopaedia of Genes and Genomes enrichment analyses revealed that these DEGs were enriched in pathways involving carbohydrate metabolism, amino acid metabolism, the immune system, the digestive system, the lysosome, and endocytosis. A total of 16 DEGs were randomly selected to further validate the accuracy of RNA-Seq dataset by reverse-transcription quantitative polymerase chain reaction. This study provides substantial transcriptomic information regarding the SG of D. citri in response to CLas infection, which may shed light on the molecular interaction between D. citri and CLas, and provides new ideas for the prevention and control of citrus psyllid.

As an environmental factor, temperature impacts the distribution of species and influences interspecific competition. The molecular chaperones encoded by small heat shock proteins (sHsps) are essential for rapid, appropriate responses to environmental stress. This study focuses on Hsp20.8, which encodes a temperature-responsive sHsp in Liriomyza trifolii, an insect pest that infests both agricultural and ornamental crops. Hsp20.8 expression was highest at 39℃ in L. trifolii pupae and adults, and expression levels were greater in pupae than in adults. Recombinant Hsp20.8 was expressed in Escherichia coli and conferred a higher survival rate than the empty vector to bacterial cells exposed to heat stress. RNA interference experiments were conducted using L. trifolii adults and prepupae and the knockdown of Hsp20.8 expression increased mortality in L. trifolii during heat stress. The results expand our understanding of sHsp function in Liriomyza spp. and the ongoing adaptation of this pest to climate change. In addition, this study is also important for predicting the distribution of invasive species and proposing new prevention and control strategies based on temperature adaptation.

Mosquito-borne diseases have emerged in North Borneo in Malaysia due to rapid changes in the forest landscape, and mosquito surveillance is key to understanding disease transmission. However, surveillance programmes involving sampling and taxonomic identification require well-trained personnel, are time-consuming and labour-intensive. In this study, we aim to use a deep leaning model (DL) to develop an application capable of automatically detecting mosquito vectors collected from urban and suburban areas in North Borneo, Malaysia. Specifically, a DL model called MobileNetV2 was developed using a total of 4880 images of Aedes aegypti, Aedes albopictus and Culex quinquefasciatus mosquitoes, which are widely distributed in Malaysia. More importantly, the model was deployed as an application that can be used in the field. The model was fine-tuned with hyperparameters of learning rate 0.0001, 0.0005, 0.001, 0.01 and the performance of the model was tested for accuracy, precision, recall and F1 score. Inference time was also considered during development to assess the feasibility of the model as an app in the real world. The model showed an accuracy of at least 97%, a precision of 96% and a recall of 97% on the test set. When used as an app in the field to detect mosquitoes with the elements of different background environments, the model was able to achieve an accuracy of 76% with an inference time of 47.33 ms. Our result demonstrates the practicality of computer vision and DL in the real world of vector and pest surveillance programmes. In the future, more image data and robust DL architecture can be explored to improve the prediction result.

Reticulitermes chinensis Snyder is an important pest in forestry and construction and is widely distributed in China. We found that Serratia marcescens Bizio strain SM1 has insecticidal activity to R. chinensis, but the pathogenic mechanism of SM1 to R. chinensis is not clear. Therefore, full-length transcriptome sequencing was performed on R. chinensis infected with SM1 and the control group. A total of 230 differentially expressed genes were identified by comparing SM1 infection group and the control group, among which 103 were downregulated and 127 were upregulated. We found downregulated genes in nine metabolic pathway categories, among which carbohydrate metabolism had the most downregulated genes, followed by energy metabolism and amino acid metabolism. We also found that some downregulated genes were related to pattern recognition receptors, cellular immunity, and humoral immunity, indicating that R. chinensis immunity was negatively affected by SM1 infection. In addition, some genes in signal transduction and genetic information processing pathways were downregulated. In this study, high-throughput full-length transcriptome analysis was used to analyse the pathogenic mechanism of SM1 to R. chinensis. The results of this study provide useful information for exploring the relationship between SM1 and R. chinensis, and provide theoretical support for the future application of SM1 and the prevention and treatment of R. chinensis.

Aspongopus chinensis Dallas 1851, an insect of important economic value, faces challenges in artificial breeding due to mandatory diapause and limited access to wild resources. Heat shock proteins (Hsps) are thought to influence diapause in insects, but little is known about their role in A. chinensis during diapause. This study used genomic methods to identify 25 Hsp genes in A. chinensis, including two Hsp90, 14 Hsp70, four Hsp60 and five small Hsp genes, were located on seven chromosomes, respectively. The gene structures among the same families are relatively conserved. Meanwhile, the motif compositions and secondary structures of A. chinensis Hsps (AcHsps) were predicted. RNA-seq data and fluorescence quantitative PCR analysis showed that there were differences in the expression patterns of AcHsps in diapause and non-diapause stages, and AcHsp70-5 was significantly differentially expressed in both analysis, which was enriched in the pathway of response to hormone. All the results showed that Hsps play an important role in the diapause mechanism of A. chinensis. Our observations highlight the molecular evolution of the Hsp gene and their effect on diapause in A. chinensis.

Since metabolism, survival, and reproduction in hexapods are closely related to temperatures; changes in the mean and variance of temperature are major aspects of global climate change. In the typical context of biological control, understanding how predator-prey systems are impacted under thermal conditions can make pest control more effective and resilient. With this view, this study investigated temperature-mediated development and predation parameters of the predator Harmonia axyridis against the potential prey Spodoptera litura. The age-stage, two-sex life table of the predator was constructed at four temperatures (i.e. 15, 20, 25, and 30°C) by feeding on the first instar larvae of S. litura. Our results showed that the mean generation time (T) decreased but the intrinsic rate of increase (r) and the finite rate of increase (λ) increased with increased temperature. The mean duration of the total preadult stage decreased with higher temperatures. The T and r were 70.47 d and 0.0769 d^-1 at 15°C; 58.41 d and 0.0958 d^-1 at 20°C; 38.71 d and 0.1526 d^-1 at 25°C; and 29.59 d and 0.1822 d^-1 at 30°C, respectively. The highest net reproductive rate (R₀) and fecundity were obtained at 25°C. The highest λ (1.1998 d^-1) and lowest T (29.59 d) were obtained at 30°C, whereas the maximum net predation rate (C₀) was at 25°C. Total population and predation rates projections were the highest at 30°C. Based on these findings, we anticipate that biological control strategies for this predator release against S. litura should be attuned to warming scenarios to achieve better biocontrol functions.

Micromelalopha troglodyta (Graeser) is an important pest of poplar in China, and glutathione S-transferase (GST) is an important detoxifying enzyme in M. troglodyta. In this paper, three full-length GST genes from M. troglodyta were cloned and identified. These GST genes all belonged to the epsilon class (MtGSTe1, MtGSTe2, and MtGSTe3). Furthermore, the expression of these three MtGSTe genes in different tissues, including midguts and fat bodies, and the MtGSTe expression in association with different concentrations of tannic acid, including 0.001, 0.01, 0.1, 1, and 10 mg ml^-1, were analysed in detail. The results showed that the expression levels of MtGSTe1, MtGSTe2, and MtGSTe3 were all the highest in the fourth instar larvae; the expression levels of MtGSTe1 and MtGSTe3 were the highest in fat bodies, while the expression level of MtGSTe2 was the highest in midguts. Furthermore, the expression of MtGSTe mRNA was induced by tannic acid in M. troglodyta. These studies were helpful to clarify the interaction between plant secondary substances and herbivorous insects at a deep level and provided a theoretical foundation for controlling M. troglodyta.