梨小食心虫幼虫龄数和龄期的划分

Determination of larval instar number and duration of the Grapholitha molesta(Lepidoptera: Tortricidae)

【目的】为明确梨小食心虫Grapholitha molesta（Busck）幼虫的发育状况,以便进行预测预报及采取防治措施。【方法】试验对幼虫头壳宽、上颚宽、体长和体宽4项指标进行测量。【结果】头壳宽和上颚宽符合Dyar法则和Crosby法则并呈现明显的线性回归关系,可作为龄期划分的重要指标,确定其龄期为5龄。室内26℃温度下饲养幼虫历期约为15 d,1-4 d为1龄期、4-7 d为2龄期、6-10 d为3龄期、8-12 d为4龄期、11-15 d为5龄期。【结论】幼虫刚毛、体色、斑纹也可作为龄期划分辅助参考方法,体长和体宽变异性较大,不宜作为幼虫龄数划分的标准。

[Objectives] To determine the developmental stages of Grapholitha molesta（Busck） larvae and provide a foundation for forecasting and scientific management of this pest. [Methods] Four morphological variables were measured, including larva head capsule width, mandible width, body length and head width. [Results] Head capsule width and mandible width conformed to the Dyar and Crosby rules, as well as having an obvious linear relationship, making them important criteria for identifying larval instars. The duration of the larval stage was about 15 d when reared under laboratory conditions at 26℃. Five Grapholitha molesta larval instars could be distinguished. These were; first instar（1-4 d）, second instar（4-7 d）, third instar（6-10 d）, fourth instar（8-12 d）, fifth instar（11-14 d）. [Conclusion] Bristles, body color and markings can be used as auxiliary distinguishing criteria method when body length and width were too variable to reliably identify instars.