Chitosan samples were prepared from the shells of marine animals (crab and shrimp) and the cell walls of fungi (agaricus bisporus and aspergillus niger). Fourier-transform infrared spectroscopy (FT-IR) was used to detect their molecular structures, while headspace-gas chromatography–ion mobility spectrometry (HS-GC-IMS) was employed to analyze their odor composition. A total of 220 volatile organic compounds (VOCs), including esters, ketones, aldehydes, etc., were identified as the odor fingerprinting components of chitosan for the first time. A principal component analysis (PCA) revealed that chitosan could be effectively identified and classified based on its characteristic VOCs. The sum of the first three principal components explained 87% of the total variance in original information. An orthogonal partial least squares discrimination analysis (OPLS-DA) model was established for tracing and source identification purposes, demonstrating excellent performance with fitting indices R²X = 0.866, R²Y = 0.996, Q² = 0.989 for independent variable fitting and model prediction accuracy, respectively. By utilizing OPLS-DA modeling along with a heatmap-based tracing path study, it was found that 29 VOCs significantly contributed to marine chitosan at a significance level of VIP > 1.00 (p < 0.05), whereas another set of 20 VOCs specifically associated with fungi chitosan exhibited notable contributions to its odor profile. These findings present a novel method for identifying commercial chitosan sources, which can be applied to ensure biological safety in practical applications.

Sarcophagidae are often the first sarcosaprophagous insects to colonize corpses in specialized cases such as indoor discoveries and burials, making them forensically crucial for estimating the minimum postmortem interval (PMI_min). Among these, Sarcophaga princeps Wiedemann (Diptera: Sarcophagidae) is a prominent species frequently associated with both buried and indoor bodies. In this study, the development time of S. princeps from larvae to adults at constant temperatures of 16, 19, 22, 25, 28, 31, and 34 °C was studied, and the times required were 1090.00 ± 57.65, 721.00 ± 8.72, 562.33 ± 27.21, 416.67 ± 27.70, 356.33 ± 16.01, 327.00 ± 7.94, and 313.67 ± 5.69 h, respectively, demonstrating a significant inverse relationship with temperature. Various developmental models were constructed using the basic developmental data, including the isomorphen diagram, isomegalen diagram, nonlinear thermodynamic Optim SSI model, and logistic regression model. These models enable the estimation of the developmental age of the specimens. In addition, the lower critical thermal threshold (T_L), intrinsic optimum temperature (T_Φ), and upper critical thermal threshold (T_H) estimated by the nonlinear thermodynamic Optim SSI model were 11.11 °C, 21.85 °C, and 35.88 °C. This study provides comprehensive developmental data of S. princeps for PMI_min estimation.

Chrysomya megacephala, as one of the common blowflies, displays biological characteristics, such as ovoviviparity and carrion-feeding adaptation. Thus, this species is generally considered of significant ecological, medical, and forensic importance. However, without a high-quality pseudo-chromosome genome for C. megacephala, elucidating its evolutionary trajectory proved difficult. Herein, we assembled and analyzed a high-quality chromosome-level genome assembly of the C. megacephala, combined with PacBio HiFi long reads, Hi-C data, and Illumina reads. The pseudo-chromosomes assembly of C. megacephala spans 629.44 Mb, with 97.05% anchored to five chromosomes. Final assembly includes 1056 contigs (N50 = 1.68 Mb), and 97 scaffolds (N50 = 121.37 Mb), achieving 98.90% BUSCO completeness (n = 1367). Gene annotation predicted 17,071 protein-coding genes (95.60% BUSCO completeness), while repeat masking identified 244.26 Mb (38.82%) as repetitive elements. Additionally, 3740 non-coding RNAs were characterized. Gene family analyses resulted in 10,579 gene families, containing 151 gene families that experienced rapid evolution. Comparative genomic analyses showed that the expanded genes are related to reproduction and necrophagous habits. In addition, we annotated the gene family P450s, CCEs, IRs, GRs, and ORs, all of which represent remarkable expansion, playing a crucial role in the mechanism of locating the hosts for forensic insects. Our research establishes a high-quality genome sequence to facilitate subsequent molecular investigations into significant species within forensic entomology.