| The black bean aphid, Aphis fabae Scopoli, is a worldwide pest of economic crops with polyphagous habits. A mutualistic relationship has been established during coevolution between aphid hosts and the primary endosymbiotic bacteria Buchnera. The host aphids provide habitats and some necessary nutrition for the bacteria while the later produce essential amino acids that are absent in phloem sap from nonessential amino acids like glutamate, which host aphids can not do this alone. It is argued that the external factors affecting host aphids should also influence their endosymbionts. However, most of studies have been contributed to understanding the aphid-Buchnera physiological interaction while much less have been done with ecological interaction between external factors and endosymbionts. The main objective of this study is to search for the relationship between some ecological factors and abundance dynamic of mycetocytes in host aphids.1. Effects of temperatures on the abundance of mycetocytes and body sizes of Aphis fabae ScopoliTo explore the effect of breeding temperature on the endosymbiotic bacteria in Aphis fabae Scopoli and body size of their hosts, the changes in the abundance of mycetocytes and host body size under different temperatures (15℃, 20℃, 25℃, 30℃ and 35℃) were observed in the laboratory. The results showed that the effect of temperature on the abundance of mycetocytes was dependent on the developmental stage of aphids. The abundance of mycetocytes in the 1st instar nymphs of the aphid showed no difference at different temperatures except at 25℃ and 35℃, but showed significant difference in the other life stages of the aphid at different temperatures, and a negative correlation between the abundance of mycetocytes and temperature was found. Temperature also affected, to some extent, the trend of the abundance of mycetocytes following the development of aphids. The abundance of mycetocytes increased with the development from nymph to...
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