桔小实蝇幼虫龄期鉴别初步研究

为明确桔小实蝇幼虫龄期的鉴别依据和划分标准。本研究将桔小实蝇幼虫置于25±1℃、60%~70%RH条件下饲养,幼虫发育历期约为6~8 d,观察各龄幼虫的前气门、后气门、头咽骨和口钩等形态特征,并对桔小实蝇幼虫口钩长、口钩宽、体长和体宽4个形态指标进行测量。桔小实蝇幼虫分为3个龄期,各龄幼虫在形态特征上存在明显差异,口钩长度和宽度在龄期之间存在显著差异,1、2、3龄幼虫口钩平均长度分别为0.0846±0.0005 mm、0.1512±0.0013 mm、0.2913±0.0015 mm,口钩平均宽度分别为0.0116±0.0003 mm、0.0308±0.0007 mm、0.0677±0.0013 mm,皆明显分为3个范围且互不重叠,口钩长和口钩宽与龄数之间符合指数回归模型,口钩长符合y=0.045e~(0.6182x),口钩宽符合y=0.005e~(0.8816x)。因此口钩可作为幼虫龄期鉴别和划分的重要形态特征,幼虫体长、体宽因重叠严重、变异性大,不适合作为龄期划分的标准。

Preliminary investigation on the identification of the larval stages of the Bactrocera dorsalis Hendel

To determine the larval stages of Bactrocera dorsalis (Hendel),we report here the preliminary investigation results on the identification and standard.The larva of B.dorsalis was reared under laboratory conditions at 25±1 °°,60％-70％RH with development duration of about 6-8 days.Morphological characters were observed,including anterior spiracle,posterior spiracle,cephalopharyngeal skeleton and mouth hook.Then,four morphological characters were measured,including mouth hook length,mouth hook width,body length and body width.The results showed that there were three instars during the larval stage with extremely different morphological characters.The mouth hook length and width for the 1st,2nd and 3rd instars were distinct with the average of 0.0846±0.0005 mm,0.1512±0.0013 mm,0.2913±0.0015 mm and 0.0116±0.0003 mm,0.0308±0.0007 mm,0.0677±0.0013 mm,respectively,which had not any overlap among larval instars.The exponential regression relationship between larval instars and mouth hook length and width was y=0.045e0.6182x and y=0.005e0.8816x,respectively.Mouth hook could be recognized as the essential morphological character for identifying and differentiating the larval instars of oriental fruit fly.Because of the overlap and the variation of body length and width,it was suggested that these characteristics be not reliable for the identification of the larval instars.