【目的】 通过观察异斑小字大蚕蛾Cricula variabilis的各虫态发育特征，掌握其基本生活史、幼虫各龄形态特征及区分方法。【方法】 在室内进行饲养观察，通过测量幼虫头壳宽、体长、体宽3个指标并计算Brooks指数和Crosby指数，结合线性回归方法对得到的数据进行拟合，确定最佳分龄指标。   【结果】 异斑小字大蚕蛾一个世代共（77.86 ± 1.09）d，蛹期占29.44%，卵期占14.46%，成虫期占6.19%。幼虫共6龄，历期最长，占整个世代的49.91%，且每个龄期随虫龄的增长而增加。运用Dyar法则与Crosby生长法则验证了头壳宽是幼虫最合理的分龄指标。通过对头壳宽、体长、体宽3个分龄指标的进行线性回归方法分析，头壳宽的指数、二次、三次线性方程来划分幼虫龄期的效果较优，其回归方程分别为y = 0.103 8x²－0.026 2x + 0.735 8（R² = 0.996 5）、y = 0.572 6e^{0.340 4x}（R² = 0.995 6）、y = 0.001 5x³ + 0.087 9x² + 0.021 8x + 0.697 6（R² = 0.996 5）。【结论】 本研究描述了异斑小字大蚕蛾各龄期幼虫的形态特征，和明确幼虫共6龄，头壳宽是幼虫分龄最合适的指标。

[Objectives]  To describe the development of Cricula variabilis and elucidate the life cycle, morphological characteristics and larval instars of this species. [Methods]  Head capsule width, body length and body width, of larvae were measured to calculate Brooks and Crosby ratios. A linear regression model was then fitted to the data to determine the best criteria for instar separation. [Results]  A generation of C. variabilis persists for a total of (77.86 ± 1.09) d, 29.44% of which is comprised of the pupal stage, 14.46% by the egg stage, 6.19% by the adult stage and 49.91% by the larval stage. The larval stage has six instars, which can be distinguished on the basis of head capsule width according to Dyar’s and Crosby rules. The duration of each successive instar is longer than that of the preceding instar. Exponential, quadratic and cubic linear models of head capsule width provided the best estimates the larval age. The relationship between head capsule width and larval instar was best explained by the equations: y = 0.103 8x² - 0.026 2x + 0.735 8 (R² = 0.996 5), y = 0.572 6e^{0.340 4x} (R² = 0.995 6), y = 0.001 5x³ + 0.087 9x² + 0.021 8x + 0.697 6 (R² = 0.996 5). [Conclusion]  A single generation of C. variabilis persists for (77.86 ± 1.09) d, 49.91% of which is comprised of the larval stage. The latter has a total of 6 instars which are best distinguished on the basis of head capsule width.