绿豆象幼虫虫龄的划分及末龄幼虫头部形态和感器观察

【目的】明确绿豆象Callosobruchus chinensis幼虫的龄期,了解其末龄幼虫头部感受器的种类、形态和分布。【方法】测量绿豆象幼虫体长、头壳宽和上颚宽,根据所得数据的频次分布图、关系拟合结果和戴氏法则确定绿豆象最佳分龄指标,明确幼虫虫龄数,并利用Crosby生长法则和线性回归的方法进行验证;采用扫描电镜对末龄幼虫头部形态及感受器进行观察。【结果】绿豆象体长、头壳宽和上颚宽的频次分布均呈显著的4个峰,因此推断绿豆象幼虫为4个虫龄。各龄的体长变幅分别为1.581～2.556, 2.406～3.381, 3.381～4.281和4.206～4.881 mm,头壳宽度变幅分别为0.444～0.689, 0.654～0.934, 0.934～1.179和1.144～1.389 mm,上颚宽变幅分别为0.080～0.256, 0.234～0.344, 0.322～0.542和0.542～0.652 mm。体长、头壳宽和上颚宽均符合戴氏法则和Crosby生长法则,并呈现明显的线性关系,因此体长、头壳宽和上颚宽可作为绿豆象幼虫龄期划分的重要指标。头壳宽的Crosby指数均小于体长和上颚宽的Crosby指数,且头壳宽与体长测量值的对数值与幼虫龄期的相关系数要优于上颚宽测量值的对数值与幼虫龄期的相关系数,因此可将头壳宽作为最佳分龄指标。绿豆象末龄幼虫头部感器共有锥形感器、毛形感器、瓶形感器、刺形感器、板形感器、栓锥形感器和坛形感器7种感器,主要分布于触角、下颚须、上唇和上颚。【结论】绿豆象幼虫分龄形态指标和头部形态观察为研究其行为活动及综合防治提供理论基础。

Determination of larval instars and the observation of head morphology and sensilla of thefinal instar larva ofCallosobruchus chinensis(Coleoptera: Bruchidae)

【Aim】 This study aims to clarify the number of larval instars and to understandthe types, morphology and distribution of sensilla on the final instar larval head of theadzuki bean beetle, Callosobruchus chinensis. 【Methods】 The body length, head capsule width and mandible width of C. chinensis larvae were measured. Based on the frequencyhistograms, regression relationship and Dyar’s rule of the obtained data, the optimalmorphological index for determining the larval instars of C. chinensis was determined. Theobtained result was verified by Crosby growth rule and linear regression method. Themorphology and sensilla on the head of the final instar larva of C. chinensis were observedunder scanning electron microscope. 【Results】 The frequency histograms of the bodylength, head capsule width and mandible width of C. chinensis larvae showed four obviouspeaks, and it is so inferred that C. chinensis larvae have four instars. The four instarshad the body length range of 1.581-2.556, 2.406-3.381, 3.381-4.281 and 4.206-4.881 mm, thehead capsule width range of 0.444-0.689, 0.654-0.934, 0.934-1.179 and 1.144-1.389 mm, andthe mandible width range of 0.080-0.256, 0.234-0.344, 0.322-0.542 and 0.542-0.652 mm,respectively. The body length, head capsule width and mandible width are in accordance withDyar’s rule and Crosby growth rule, and show obvious linear relationship. Therefore, thebody length, head capsule width and mandible width can be used as important indexes for thedivision of larval instars of C. chinensis. The Crosby ratio of head capsule width issmaller than those of body length and mandible width, and the correlation coefficientbetween the logarithmic value of head capsule width and body length and larval instar ishigher than that between mandible width and larval instar, so the head capsule width can beused as the optimal index for the division of larval instars. Seven types of sensillaincluding sensillum basiconicum, sensillum trichodeum, sensillum lageniform, sensillumchaeticum, sensillum placodeum, sensillum styloconicum and sensillum ampullaceum wereobserved on the head and are mainly located on the antennae, maxillary palp, labrum andmandible. 【Conclusion】 The morphological indexes of the division of larval instars andthe observation of head morphology and of the C. chinensis provide a theoretical basis forthe study of behavior and integrated control.