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S-(-)-trans-Verbenol (1) and its antipode, R-(+)-trans-verbenol (1') have been confirmed as the critical pheromone components of bark beetles. Synthesis of these two active secondary alcohols (1 and 1') from commercially available starting materials S-α-pinene and R-α-pinene was reported. The key steps were mainly depended on the effective SN2 stereo-inversion of the hydroxy group of sterically hindered alcohols (3 and 3'), using Mitsunobu reaction or hydrolysis of mesylate ester, alternatively. Our results provide a new and stereo-selectivity way to obtain optically active insect pheromones.

The larvae of Ips typographus and Ips subelongatus can cause extensive damage to coniferous trees under their bark, resulting in severe economic losses within the forestry industry. In this study, we analyzed and compared the sensilla on the antennae and mouthparts of the larvae of these two species to identify biology- and taxonomy-related differences using scanning electron microscopy. In general, no significant differences in sensilla type or distribution on the antennae and mouthparts of the larvae were observed between the two species. However, some sensilla lengths, basal widths, and quantities varied greatly between the species. Two types of sensilla were observed on the antennae: sensilla basiconica (B.a.1) and sensilla twig basiconica (T.b.1 and T.b.2). The mouthparts had five types of sensilla: sensilla trichodea (T.r.1 and T.r.2), sensilla chaetica (C.h), B.a.2, T.b.3–T.b.5, and sensilla placodea (P.l). We also discuss the function of each type of sensilla based on their morphologies and locations. The results provide a theoretical basis for further studies on the electrophysiology and feeding behaviors of I. typographus and I. subelongatus larvae.

Background Micromelalopha siversi (Staudinger) (Lepidoptera: Notodontidae) is a defoliator of poplar trees, Populus spp. (Salicaceae). In our previous study, 13,15-octadecadienal has been conformed as a female-produced candidate sex pheromone component of M. siversi, but the Z/E stereochemistry of the 1,3-diene system has not been identified so far. Results Four unsaturated aliphatic aldehydes, Z13,E15-18:Ald, Z13,Z15-18:Ald, E13,E15-18:Ald, and E13,Z15-18:Ald, were synthesized from the commercially available 12-bromo-1-decanol mainly by alkylation of lithium alkyne, normal Wittig or Wittig-Schlosser olefination, and hydroboration-protonolysis. According to gas chromatography (GC) analysis of pheromone gland extracts, Z13,E15-18:Ald was the main component, and a small amount of Z13,Z15-18:Ald was also detected, with a ratio of approximately 7:3. However, the results of GC-electroantennographic detection (GC-EAD) showed that Z13,E15-18:Ald was the only compound with electrophysiological activity, whereas Z13,Z15-18:Ald elicited no activity. In the field, traps baited with only Z13,E15-18:Ald resulted in much superior results to those with Z13,Z15-18:Ald as well as the Z13,E15-18:Ald and Z13,Z15-18:Ald binary mixture. Conclusions Based on geometrically selective synthesis and bioactivity tests, the active sex pheromone component of M. siversi has been identified as Z13,E15-18:Ald, the pheromone component that has not been identified in Lepidoptera before. The synthetic component was attractive to male moths in preliminary field traps, which provides novel technologies to monitor and control this pest.

BACKGROUND Micromelalopha siversi (Staudinger) (Lepidoptera: Notodontidae) is a defoliator of poplar trees, Populus spp. (Salicaceae). In our previous study, 13,15‐octadecadienal has been conformed as a female‐produced candidate sex pheromone component of M. siversi, but the Z/E stereochemistry of the 1,3‐diene system has not been identified so far. RESULTS Four unsaturated aliphatic aldehydes, Z13,E15‐18:Ald, Z13,Z15‐18:Ald, E13,E15‐18:Ald, and E13,Z15‐18:Ald, were synthesized from the commercially available 12‐bromo‐1‐decanol mainly by alkylation of lithium alkyne, normal Wittig or Wittig–Schlosser olefination, and hydroboration‐protonolysis. According to gas chromatography (GC) analysis of pheromone gland extracts, Z13,E15‐18:Ald was the main component, and a small amount of Z13,Z15‐18:Ald was also detected, with a ratio of approximately 7:3. However, the results of GC‐electroantennographic detection (GC‐EAD) showed that Z13,E15‐18:Ald was the only compound with electrophysiological activity, whereas Z13,Z15‐18:Ald elicited no activity. In the field, traps baited with only Z13,E15‐18:Ald resulted in much superior results to those with Z13,Z15‐18:Ald as well as the Z13,E15‐18:Ald and Z13,Z15‐18:Ald binary mixture. CONCLUSIONS Based on geometrically selective synthesis and bioactivity tests, the active sex pheromone component of M. siversi has been identified as Z13,E15‐18:Ald, the pheromone component that has not been identified in Lepidoptera before. The synthetic component was attractive to male moths in preliminary field traps, which provides novel technologies to monitor and control this pest., The sex pheromone of Micromelalopha siversi was characterized as (13Z,15E)‐octadecadienal, the pheromone component that has not been identified in Lepidoptera before. The total synthesis of this active component was also reported. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Simple Summary Many bark beetles are destructive pests in coniferous forests and cause extensive ecological and economic losses worldwide. Comparative studies of the structural characteristics of mitogenomes and phylogenetic relationships of bark beetles can improve our understanding of mitogenome evolution. In this study, we sequenced eight mitogenomes of bark beetles. Our results show that the use of start and stop codons, the abundance of amino acids, and the relative frequency of codon use are conserved among the eight bark beetles. Different regions of tRNA exhibit different degrees of conservatism. Together with the analysis of evolutionary rates and genetic distance among bark beetle species, our results reveal phylogenetic relationships among bark beetles of the subfamily Scolytinae. Abstract Many bark beetles of the subfamily Scolytinae are the most economically important insect pests of coniferous forests worldwide. In this study, we sequenced the mitochondrial genomes of eight bark beetle species, including Dendroctonus micans, Orthotomicus erosus, Polygraphus poligraphus, Dryocoetes hectographus, Ips nitidus, Ips typographus, Ips subelongatus, and Ips hauseri, to examine their structural characteristics and determine their phylogenetic relationships. We also used previously published mitochondrial genome sequence data from other Scolytinae species to identify and localize the eight species studied within the bark beetle phylogeny. Their gene arrangement matched the presumed ancestral pattern of these bark beetles. Start and stop codon usage, amino acid abundance, and the relative codon usage frequencies were conserved among bark beetles. Genetic distances between species ranged from 0.037 to 0.418, and evolutionary rates of protein-coding genes ranged from 0.07 for COI to 0.69 for ND2. Our results shed light on the phylogenetic relationships and taxonomic status of several bark beetles in the subfamily Scolytinae and highlight the need for further sequencing analyses and taxonomic revisions in additional bark beetle species.

Chitinases, which are crucial enzymes required for chitin degradation and reconstruction, are often selectively considered to be effective molecular targets for pest control due to their critical roles in insect development. Although the Hyphantria cunea chitinase gene has been reported previously, its sequence characteristics, gene function, and feasibility as a potential target for pest management were absent. In the present study, we characterized the H. cunea chitinase gene and designated it HcCht5. Phylogenic and domain structure analysis suggested that HcCht5 contained the typical chitinase features and was clustered into chitinase group I. Tissue-specific and developmental expression pattern analysis with Real-Time Quantitative PCR (RT-qPCR) showed that HcCht5 was mainly expressed in the integument tissues and that the transcript levels peaked during molting. RNA interference (RNAi)-mediated silencing of HcCht5 caused 33.3% (2 ug) and 66.7% (4 ug) mortality rates after double-stranded RNA (dsRNA) injection. Importantly, the interference efficiency of HcCht5 depended on the injection time of double-stranded RNA (dsRNA), as the pre-molting treatment achieved molt arrest more effectively. In addition, transcriptome sequencing (RNA-seq) analysis of RNAi samples demonstrated silencing of the down-regulated HcCht5 genes related to chitin metabolism and molting hormone signaling, as well as genes related to detoxification metabolism. Our results indicate the essential role of HcCht5 in H. cunea development and detail the involvement of its gene function in the larval molting process.