Chemosensory systems play a pivotal role in insect survival and reproduction by mediating the detection of volatile organic compounds in the environment. Protaetia brevitarsis (Coleoptera: Scarabaeidae), a phytophagous pest widely distributed across East Asia, poses a significant threat to agro-horticultural systems through crop damage. We conducted antennal transcriptome sequencing of adult beetles and identified 117 chemosensory-related genes, including 66 odorant receptors (ORs), 20 ionotropic receptors, 10 gustatory receptors, 13 odorant-binding proteins (OBPs), four chemosensory proteins, and four sensory neuron membrane proteins. Tissue-specific expression profiling revealed the antennal enrichment of five PbreOBP genes and twenty-three ORs. Notably, sexual dimorphism was observed in OR expression patterns. PbreOR1/6/17/18/21/22/30/32 exhibited male-biased antennal expression, whereas PbreOR25/26/29/38/41/44/61 demonstrated female-biased antennal expression, indicating their potential involvement in sex-specific behaviors, such as pheromone detection and oviposition site selection. A comprehensive description of the antenna chemosensory-related genes of P. brevitarsis has deepened our understanding of the olfactory mechanisms in coleopteran insects. This study also provides a basis for understanding the molecular mechanisms underlying olfaction in P. brevitarsis.

The polyphagous pest Oxycetonia jucunda Faldermann can cause substantial damage to a range of economically important crops, with the adult beetles feeding directly on floral tissues and young leaves. RT-qPCR is widely used to analyze gene expression, for which the selection of stable reference genes is essential for enabling an accurate normalization of expression. However, no systematic evaluations of suitable reference genes for RT-qPCR analysis using different tissues of O. jucunda have been conducted. To assess their applicability as reliable normalization controls, we used five computational methods to examine the stability of seven potential reference genes (GAPDH, EF1α, RPS3, RPS18, RPL18, RPS31, and UBC5A) across six adult tissues, with three biological replicates per tissue. The findings revealed RPS3 and RPS31 to be the most stably expressed. This pair of reference genes was further validated by normalizing the expression of the odorant-binding protein 3 (OBP3) target gene. Our findings will provide important foundational data for the accurate analysis of functional gene expression in O. jucunda.

Leucoptera malifoliella (Lepidoptera: Lyonetiidae) is a quarantine pest of apple and other Rosaceae fruit trees whose range is expanding into new territories. Its minute size and morphological overlap with closely related Lyonetiidae make routine identification unreliable, especially for larvae and damaged specimens. We compared COI sequences from six common small Lepidoptera species found in orchards and designed the species-specific primer pair SXW-F/SXW-R. The resulting polymerase chain reaction (PCR) assay amplifies an ~500 base pairs (bp) fragment exclusively from L. malifoliella; no product was detected in any of five non-target species. The reaction tolerates annealing temperatures of 50–58 °C and consistently detects the target across all life stages (first- to third-instar larvae, pupae, adults) and all adult tissues tested (antennae, head-thorax, abdomen, wings, legs). Detection sensitivity reaches 0.03 ng/μL—approximately one-thousandth of the DNA content of a single adult. This is the first species-specific COI (SS-COI) method reported for L. malifoliella. It furnishes a rapid, specific, and sensitive diagnostic tool for quarantine inspection, field monitoring, and integrated pest management (IPM) programs.