【目的】 鳞翅目害虫幼期区分性别的研究报道较少，本文以4种重要鳞翅目害虫草地贪夜蛾Spodoptera frugiperda、斜纹夜蛾Spodoptera litura、玉米螟Ostrinia furnacalis和二化螟Chilo suppressalis为对象，探究了其幼虫期和蛹期雌雄区分的方法。【方法】 通过解剖学和形态学观察，对4种害虫幼虫期的睾丸和卵巢，以及雌雄蛹的形态特征进行比较分析。【结果】 4种害虫幼虫期的睾丸和卵巢都处于第2腹足到第3腹足近背面位置，睾丸左右并列呈肾形结构，卵巢左右并列为椭圆形结构，可以以睾丸的有无来判断其幼虫的雌雄；4种害虫雌蛹的产卵孔和生殖孔连接成一条短裂缝，而雄蛹在生殖孔内有2个半圆形的瘤状突起。【结论】 通过解剖睾丸的有无可判断4种害虫幼虫的雌雄，观察蛹尾部生殖孔附近有无一对半圆形的瘤状突起可区分蛹的雌雄。研究结果对指导害虫预测预报以及后续科学研究的顺利进行具有指导意义。

[Aim]  To investigate methods of identifying the sex of the larvae and pupae of four key lepidopteran pests, Spodoptera frugiperda, Spodoptera litura, Ostrinia furnacalis and Chilo suppressalis. [Methods]  Morphological characteristics of the testes and ovaries of the larvae of the four pest species, as well as male and female pupae, were compared. [Results]  The testes and ovaries of the larval stages of all four pests were located near the dorsal surface in the second to third abdominal segment. The testes are juxtaposed in a kidney-shaped structure and the ovaries are juxtaposed in an elliptical structure during the larval stage. [Conclusion]  The presence or absence of testes was sufficient to determine the sex of larvae. Female pupae had an ovipositor orifice and gonopore connected into a short slit, whereas male pupae had two semicircular tumor-like projections on the gonopore. Therefore, male and female larvae of all four pest species could be distinguished by dissection to determine the presence or absence of testes, and male and female pupae could be distinguished by observing the presence, or absence, of a pair of semicircular tubercle-like projections near the caudal gonopore. Identifying the sex of larvae and pupae is useful for prediction and forecasting, and for laboratory research.