Dianyu Liu

Imperata cylindrica is a highly invasive grass that causes severe ecological and agricultural damage worldwide, yet effective and sustainable management options remain limited. In this study, we investigated insects associated with the stems and rhizosphere soil of I. cylindrica in four parks in Beijing, China, and evaluated the utility of DNA barcoding for species identification and natural enemy discovery. A total of 16 insect samples were collected, and the mitochondrial COI gene was amplified using universal (LCO1490/HCO2198) and degenerate (KC-COI-F/R) primers. High-quality sequences were obtained from 12 of the 16 individual specimens, representing two classes (Insecta and Symphyla), two orders (Diptera and Coleoptera), and five families (Chloropidae, Muscidae, Rhiniidae, Eumolpidae, and Scutigerellidae). Chloropidae larvae (Diptera) dominated the stem-associated samples, and Pseudocolaspis sp. (Coleoptera: Eumolpidae), Atherigona orientalis (Diptera: Muscidae), Rhyncomya pruinosa (Diptera: Rhiniidae), and a species of Scutigerellidae (Symphyla) were also identified. BLAST analysis assigned the chloropid sequences to Chloropidae sp. BIOUG02404-H03 with 96.93–97.34% identity, and these sequences were recovered from stems at all four sampling sites. These results demonstrate that DNA barcoding effectively identifies morphologically challenging immature stages and soil-dwelling specimens. The abundant chloropid larvae, which feed internally in I. cylindrica stems, represent a promising candidate for further host-specificity testing as a classical biological control agent. This study provides the first molecular characterization of insects associated with I. cylindrica in Beijing and highlights the value of DNA barcoding in biocontrol resource discovery.

Chitin synthase (CHS) is essential for maintaining exoskeletal integrity and environmental adaptability in insects. CHS genes are categorized into two types, CHS1 and CHS2. Hemipteran insects possess only the CHS1 gene due to the absence of a peritrophic matrix (PM) in their midgut. However, the identification and functional characterization of the CHS1 gene in Pentatomidae species have not been reported. This study reports the first identification of a CHS gene, ArmaCHS1, from the predatory stink bug, Arma chinensis, and investigates its role in response to temperature stress. The ArmaCHS1 open reading frame spans 4407 bp, encoding a protein of 1468 amino acids, with 14 transmembrane helices and seven N-glycosylation sites. Phylogenetic analysis confirmed its classification within the CHS1 clade, closely related to CHS1 from Halyomorpha halys. qRT-PCR analysis revealed that ArmaCHS1 is predominantly expressed in the exoskeleton and displays developmentally regulated expression (lowest in eggs, highest in adults). Temperature stress experiments demonstrated that ArmaCHS1 expression was significantly upregulated at low temperatures (12 °C, 19 °C) and markedly downregulated at high temperatures (33 °C, 40 °C). These findings indicate that ArmaCHS1 likely contributes to thermal adaptation in A. chinensis by modulating chitin biosynthesis, providing new insights into the environmental stress responses of beneficial predatory insects.

Fatty acids are the main form of energy production and storage in insects, and fatty acid synthase (FAS) plays a major role in this process. Arma chinensis is a natural enemy used in China to control agricultural pests. While its whole genome has been assembled, its FAS genes remain undescribed. Herein, we aim to identify the FAS genes of A. chinensis and explore their expression during starvation. Phylogenetic analysis identified nine FAS genes (ArmaFas1–ArmaFas9). During the predatory developmental stages, ArmaFas9 expression gradually increased from the 2nd to the 4th instar, peaking at the 5th instar and plateauing at the adult stage. Female adults exhibited the highest expression of ArmaFas9 in their fat body and the lowest expression in their salivary glands, whereas male adults demonstrated the opposite pattern. ArmaFas9 expression was negatively correlated with starvation duration. Compared to the controls, starved adult females exhibited a downward expression trend, whereas starved adult males demonstrated an initial increase, followed by a downward trend after 7 days. Starvation and refeeding increased ArmaFas9 expression. These results demonstrate the important role of ArmaFas9 in A. chinensis growth and development, providing a basis for further studies on lipid synthesis in predatory bugs.