Abstract:  【Aim】 This study aims to accurately determine the instars of the soybean aphid, Aphis glycines based on morphological characteristics. 【Methods】 Eight morphological indices of the wingless and winged A. glycines, including body length, body width, head width, the number of antennal segments, antenna length, cornicle length, cauda length and hind tibia length, were measured under the ultrawide area 3D microscope. 【Results】 The results indicated that the morphological characteristics are different among various instars of both wingless and winged A. glycines. The hind tibia length and cauda length of the wingless individuals and the hind tibia length, body length, antenna length, cauda length of the winged individuals displayed either no or low overlap between adjacent instars and thus could be regarded as remarkable criteria to identify instars of both morphs. Additionally, the cauda shape could be regarded as the representative morphological characteristics to differentiate the nymph and adult, and the number of antennal segments could be regarded as the morphological characteristics to differentiate the 1st instar nymph, 2nd instar nymph and the other instars. 【Conclusion】 The instars of A. glycine can be accurately and quickly identified according to the hind tibia length and cauda length of the wingless individuals and the comprehensive analysis about the hind tibia length, body length, antenna length and cauda length of the winged individuals. In addition, such morphological indices as the number of antennal segments, shape of cauda, body width, cornicle length and wing pad development facilitate the instar identification of this insect.

Key words: Aphis glycines, instar, morphological characteristics, winged morph, wingless morph