Sukovata Lidia
Department of Forest Protection, Forest Research Institute, 3, Braci Leśnej St., Sękocin Stary, 05-090 Raszyn, Poland.
Insects. 2019 Nov 2;10(11):384. doi: 10.3390/insects10110384.
The number of larval instars is important from both theoretical and practical perspectives. Three previous studies based on head capsule widths (HCWs) have suggested that larvae pass through seven instars, but the estimated HCW means differed greatly. Various methods are available for determining the number of instars; however, these methods have not been compared on the same dataset. Therefore, the main goal of this study was to compare three approaches for instar separation in larvae: visual approach followed by non-linear least squares (NLLS) estimation, kernel density estimation (KDE) followed by NLLS, and model-based clustering. Two criteria were used to assess whether the resulting instar separations adhered to Brooks-Dyar's rule: Crosby's growth rule and a coefficient of determination indicating the goodness of fit of a straight line to the ln-transformed mean HCW of the respective instars. Our results showing that larvae pass through eight instars differed greatly from reports in the literature. The best results were obtained by KDE followed by NLLS. For proper instar separation, both criteria of Brooks-Dyar's rule must be met.
幼虫龄期的数量从理论和实践角度来看都很重要。之前三项基于头壳宽度（HCW）的研究表明，幼虫经历七个龄期，但估计的HCW平均值差异很大。有多种方法可用于确定龄期数量；然而，这些方法尚未在同一数据集上进行比较。因此，本研究的主要目标是比较三种用于幼虫龄期分离的方法：先采用视觉方法然后进行非线性最小二乘法（NLLS）估计、先采用核密度估计（KDE）然后进行NLLS估计以及基于模型的聚类。使用两个标准来评估所得的龄期分离是否符合布鲁克斯 - 戴尔规则：克罗斯比生长规则和一个决定系数，该系数表明直线与各龄期经自然对数变换后的平均HCW的拟合优度。我们的结果表明幼虫经历八个龄期，这与文献中的报道有很大差异。先采用KDE然后进行NLLS得到了最佳结果。为了进行适当的龄期分离，必须满足布鲁克斯 - 戴尔规则的两个标准。
