Internode borer (INB), Chilo sacchariphagus indicus has been a serious threat to sugarcane cultivation for more than six decades. We have determined the number of instars for INB through frequency distribution analysis of cast head capsule widths. This is the first report, which proves that the INB of sugarcane passes through five larval instars to attain its pupal stage. The number of instars determined by kernel density estimation was in corroboration with the number of instars observed in the laboratory. The mean Dyar’s ratios for both the instar-wise observed data on head capsule widths and the theoretical data derived from the frequency distribution analysis were one and the same (1.46). Linear regression (R² > 0.998) between the instar numbers and their corresponding mean head capsule widths reaffirmed that no instar has been overlooked. Further, the theoretical misclassification probabilities of 0.16–1.97% indicates that the chance of misidentifying an INB instar into its preceding or succeeding one is very remote. Since the determination of the exact number of instars in a pest species is a pre-requisite for developing appropriate management strategies, the outcome of this study holds great promise in managing the most notorious Crambid borer of sugarcane.

节间虫（INB），印度lo糖（Chilo sacchariphagus indicus）对甘蔗种植造成了六十多年的严重威胁。我们已经通过对铸头囊宽度的频率分布分析确定了INB的龄期数。这是第一份报告，证明甘蔗的INB穿过五只幼虫，达到了p期。通过籽粒密度估算确定的幼虫数与实验室观察到的幼虫数相符。头囊宽度的星状观测数据与频率分布分析得出的理论数据的平均Dyar比率是相同的（1.46）。线性回归（R ² （＞ 0.998）在幼龄期数与它们相应的平均头囊宽度之间的关系再次证实没有忽略幼龄期。此外，理论上的误分类概率为0.16-1.97％，这表明将INB幼龄误识别为其前一个或后一个幼龄的可能性很小。由于确定害虫物种中幼龄的确切数目是制定适当管理策略的先决条件，因此本研究的结果对于管理最臭名昭著的甘蔗C虫具有广阔的前景。