Abstract: 【Aim】 This study aims to analyze the difference in the visual ability of Rhopalosiphum padi adults by comparing the external morphology of compound eyes of five different forms (winged virginoparae, wingless virginoparae, male, oviparae and gynoparae) 
and wingless virginoparaes from holocyclic and anholocyclic life cycles, so as to provide a basis for further exploring the reproductive transformation and host searching mechanism of R. padi. 【Methods】 The external morphology and types of compound eyes in holocyclic and anholocyclic wingless virginoparae of R. padi and adults of five forms produced by the holocyclic aphids at low temperature (12℃) and short photoperiod (8L∶16D) were observed using scanning electron microscopy (SEM). 【Results】 The compound eye of adult R. padi is oval and located at the base of antenna in the head, without sensory hairs in the separation of ammatidias. There is no significant difference in the size (long axis diameter and short axis diameter) and arc height of compound eyes, the amount of ommatidia and the diameter of ommatidium between holocyclic and anholocyclic wingless virginoparae of R. padi. However, there are significant differences in the size and arc height of compound eyes, the amount of ommatidia, and the diameter of ommatidium among the five forms of R. padi with holocyclic life cycle at low temperature and short photoperiod. Male, winged virginoparae and gynoparae have larger compound eye area and a larger number of ommatidia than wingless virginoparae and oviparae, and oviparae has the smallest compound eye area and the lowest number of ommatidia.【Conclusion】 Combining the results of the five parameters, it was assumed that the visual ability of the five forms of R. padi from strong to weak is as below: male, winged virginoparae, gynoparae, wingless virginoparae and oviparae. The variances in compound eyes and ocelli might be associated with reproductive transformation and host searching of R. padi.

Key words: Rhopalosiphum padi, reproductive mode, aphid form, compound eye, morphology; scanning electron microscopy