【目的】 稻显纹纵卷叶螟Cnaphalocrocis exigua和稻纵卷叶螟Cnaphalocrocis medinalis幼虫形态特征和为害症状相似，极易混淆，限制了对二者种间竞争关系的进一步研究。为明确2种纵卷叶螟幼虫的鉴定方法，并区分这2种害虫在水稻上的生态位。【方法】 对稻显纹纵卷叶螟和稻纵卷叶螟幼虫的形态特征进行系统观察和比较，获得两种害虫的鉴定方法，并从时间和空间资源利用上分析二者在水稻上的发生分布和生态位差异。【结果】 形态特征比较发现稻显纹纵卷叶螟和稻纵卷叶螟1龄幼虫刚毛和头壳的颜色，2-5龄幼虫前胸、中胸和后胸背板纹路可作为2种幼虫的区分依据。采用鉴别方法分析2种纵卷叶螟幼虫在水稻上的发生分布，结果表明2种幼虫在叶片的上部、中部和下部的数量分布比例没有显著差异（P>0.05），但不同发生时间的数量分布比例存在显著差异（P<0.05）。2种幼虫仅在特定时间同时为害水稻时，稻显纹纵卷叶螟时间生态位宽度大于稻纵卷叶螟，二者在时间上生态位相似系数（0.181 8）和种间竞争系数（0.205 8）都较低，在时间上种间竞争不激烈；但是稻纵卷叶螟的空间生态位宽度更大，它们在空间上生态相似系数（0.958 1）和种间竞争系数（0.998 0）都较高，空间种群竞争严重。【结论】 2种纵卷叶螟在时间和空间资源利用上存在差异，二者通过对时空资源的分配实现种群共存和同源竞争。

[Objectives]  To improve the ability to identify Cnaphalocrocis exigua and Cnaphalocrocis medinalis larvae, which are morphologically very similar and cause similar types of damage to rice crops, and describe the niches of these species. [Methods] C. exigua and C. medinalis larvae were identified by systematic observation and comparison of morphological characteristics. Based on larval characteristics, the spatiotemporal distribution and niches of these species were investigated in Qianwei county, Sichuan province using a sampling survey. [Results]  Comparison of morphological characteristics indicate that the bristle color and head shells of 1st instar larvae, and the protergum, mesonotum and metanotum patterns of 2-5 instar larvae, can be used to distinguish different developmental stages of C. exigua and C. medinalis. Based on this, the spatiotemporal distribution of these two types of leaf folder larvae in rice crops was analyzed. There was no significant difference in the spatial sdistribution of these species on different parts of rice leaves (P>0.05), but there were significant differences in their temporal distribution (P<0.05). These species only cooccur on rice plants during a specific period of the year and the temporal niche breadth of C. exigua is larger than that of C. medinalis. The niche proportion similarity (0.181 8) and the interspecific competition coefficient (0.205 8) are low, and temporal interspecific competition is not intense. However, the spatial niche breadth of C. medinalis is larger, and the spatial niche proportional similarity (0.958 1) and interspecific competition coefficient (0.998 0) were high, indicating that spatial competition is intense. [Conclusion]  C. exigua and C. medinalis larvae differ in their distribution in time and space which allows both species to coexist in rice crops without intense interspecific competition.