Abstract: Primary endosymbiotic bacteria are obligate for nutritional metabolism in host aphids. Changes of mycetocytes along with aphid development in different morphs and as affected by starvation and parasitism were observed in this paper. The number and volume of mycetocytes varied with age and morph, increasing with early larval growth and then gradually declined with embryo production. The number and volume of mycetocytes were not different within 3 days after birth, but then greater in apterous than in alate morphs. The number of mycetocytes decreased linearly with starvation duration but can be recovered after feeding was resumed. Number of mycetocytes was greater in aphids parasitized by Lysiphlebus confusus on the 3^th d after parasitization than in unparasitized aphids, but then much less in the former than in the latter, dropping from 119 on the 4^th d to 46 on the 6^th d per aphid. The current results suggested that mycetocytes varied relatively with aphid morph, age, nutrition and parasitism.