圆柏大痣小蜂幼虫龄期测定

明确圆柏大痣小蜂Megastigmus sabinae Xu et He（1989）幼虫的最佳分龄指标、幼虫龄数与各虫龄龄期，为探明圆柏大痣小蜂幼虫期的生长规律奠定基础。本研究通过测量圆柏大痣小蜂幼虫上颚关节宽、头宽、体宽和体长4个形态指标，利用频次分布推测幼虫龄数，运用Crosby生长法则和线性回归的方法判断圆柏大痣小蜂幼虫的最佳分龄指标并验证幼虫的龄数。将最佳分龄指标作为龄期判断依据，根据测量结果对其幼虫龄期进行划分。圆柏大痣小蜂幼虫共划分为5个龄期，上颚关节宽为圆柏大痣小蜂幼虫龄期划分的最佳形态指标，各龄幼虫的历期约为30 d、200 d、30 d、30 d、15 d，共305 d，主要以2龄越冬。

Measurement of larval instars of Megastigmus sabinae (Hymenoptera: Megastigmidae)

Determining the best variable to separate the larval instar and ascertain the stadia of larval instars, to lay a foundation for studying the growth rhythm of the larvae of Megastigmus sabinae Xu et He (1989). In this study, we measured four morphological variables of larvae, including mandible joint width, head width, body width and body length. The number of larval instar was determined by the frequency analysis and we judged the best variable and tested the instar number by Crosby law and linear regression. Larval stadia was estimated on the base of the best variable resulted from measurement and separation. There were five instars of M. sabinae larvae, and the mandible joint width was the best morphological variable in separating the larvae instars. The larval instars were estimated to be about 30 d, 200 d, 30 d, 30 d and 15 d, totally 305 d, alive as the second instar overwinters.