Abstract:

Objective: In this study, an analysis was conducted on the geometric morphology characteristics of right forewings of 16 species of noctuid adults, which aims to provide a morphological basis for the digital classification of moths and also conduct exploratory research on insect species in the field of axial analysis. Method: Firstly, the software tpsDig2 was used to extract local landmark coordinate data in a specific order. Secondly, the Procrustes superposition analysis was conducted on the topological structure differences within and between species, and explored the degree of morphological variation of different noctuids at different landmarks. Thirdly, the data of average configuration map were visualized to explore the axial specificity of 16 species of noctuids at different landmarks. The thin plate spline analysis was used to investigate the variation trend of landmark on the right forewing of noctuids. Finally, discriminant analysis was applied to build classification function to classify and identify the noctuid insects. Result: 1) The analysis of the topological structure of landmark space showed that 16 species of noctuids exhibited high homology within species, and significant differences existed between species. 2) The Procrustes superposition diagram revealed that 16 species of noctuids exhibited a significant dispersion trend at the the crossing points of radial vein R₄, elbow vein Cu₂, and buttock vein 2A with the outer edge of the moth wing, as well as at the the crossing point of radial vein R₁ base, while their distribution was more concentrated at the the crossing points of midrib M₁, M₂, and M₃ with the outer edge of the moth wing. 3) Axial specificity analysis showed that there were morphological differences between the horizontal and longitudinal directions of the crossing points of the wing veins around the wing chambers of 16 noctuids, indicating that the inter species differences in this region were mainly reflected in the horizontal direction, while there were no significant axial differences at the crossing points of the outer edge of the moth wings. 4) Thin plate spline analysis presented the changes in the wing parts of 16 species of noctuids corresponding to 15 landmarks on the right forewing, and found that noctuids belonging to the same genus had similar trends in changes. 5) The discriminant analysis accuracy of the test samples was 98.12%, with only 3 Trisuloides c-album mistakenly classified as Trachea atriplicis, while the remaining 16 species of noctuids were correctly classified. Conclusion: There are significant differences in the dispersion degree and variation trend of 16 species of noctuid moths at different landmark points on the wing veins. The interspecific differences at landmarks around the wing chamber are mainly reflected in the horizontal direction, while the differences in the horizontal and longitutional directions at the outer edge of the wing chamber are not significant. Combined with discriminant analysis, the effectiveness and reliability of geometric morphological characteristics of moth wings in the taxonomic identification of noctuid insects are verified.

Key words: noctuid, moth wings, geometric morphology, topological structure, axial specificity