[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.