【目的】 明确不同龄期莲缢管蚜Rhopalosiphum nymphaeae的外部形态特征，以期快速鉴别莲缢管蚜各龄期。【方法】 在显微镜下观察莲缢管蚜的形态特征并测量其体长、体宽和头壳宽，其触角、腹管、尾片、后足胫节和翅基在压片后进行测量，分析比较不同龄期的形态特征。【结果】 莲缢管蚜1龄若蚜触角为4节或5节，2龄若蚜触角节数为5节，3龄若蚜触角为5节或6节，4龄及以上龄期蚜虫触角为6节。莲缢管蚜1-2龄若蚜尾片无或呈半月形至三角型，3-4龄若蚜尾片呈半月形至三角形，成蚜尾片呈圆锥状。若蚜于3龄时开始翅基分化，有翅型3龄若蚜翅基长至腹部第1节至第1节中部，有翅型4龄若蚜翅基长至腹部第2-4节。不同龄期形态特征测量值间存在差异，但是各龄期间数值分布大多有重叠，其中不重叠的数值可作为龄期鉴别的关键指标，如有翅型3-4龄若蚜的翅基长；有少量重叠的数值可作为龄期鉴别的重要指标，如无翅型1-4龄若蚜的体长；有部分重叠数值可作为龄期鉴别的辅助指标，如无翅型3-4龄若蚜的后足胫节长。【结论】 触角的节数、尾片的发育程度和翅基的有无及长短可作为莲缢管蚜龄期鉴别的关键指标，各测量指标随莲缢管蚜龄期增长而增长趋势明显，可作为莲缢管蚜龄期鉴别的参考指标。

 [Aim]  The external morphological characteristics of each Rhopalosiphum nymphaeae instar was documented to facilitate rapid instar identification for future studies. [Methods]  The morphological characteristics of R. nymphaeae were observed under the microscope, including measurements of body length, body width, and headshell width. The antennae, cornicle, cauda, hindfoot tibia, and wing base were measured after pressing. Differential and correlational analyses were carried out on the measurement data, followed by construction of box plots, to investigate the morphological variations across different developmental stages. [Results]  The antennae of 1st instar R. nymphaeae nymphs consisted of 4 or 5 segments. Similarly, 5 segments were observed in 2nd instar nymphs, while the antennae of 3rd instar nymphs had 5 or 6 segments. The antennae of 4th instar nymphs and older had 6 segments. No cauda or half-moon to triangle cauda were observed in 1st or 2nd instar nymphs, whereas half-moon to triangle cauda were observed in the 3rd and 4th instar nymphs. A cone-shaped cauda was observed in adult R. nymphaeae. In the winged morph of R. nymphaeae nymphs, differentiation of the wing base was observed to start at the 3rd instar. At this stage, the wing base extends from the first to the middle of the first ventral segment. By the 4th instar, the wing base extends further to the second to fourth ventral segment. Significant differences and correlations were observed between the morphological characteristics measured at different instars. However, the distribution of values for these characteristics tended to overlap between the different instar stages. The absence of an overlap may serve as a key indicator for age identification. For example, the wing base length of winged 3rd-4th instar nymph. A small amount of overlap can be used as an important indicator for instar identification, such as the body length of wingless 1st-4th instar nymphs. Partial overlapping values can serve as an auxiliary index for instar identification, such as the length of hindfoot tibia of wingless 3rd-4th instar nymphs. [Conclusion]  The number of antennae segments, cauda development, and the presence and length of the wing base can serve as key indices for determining the age of R. nymphaeae. The progressive increase in each index was correlated strongly with instar stage, providing a reliable reference index for determining R. nymphaeae age.