| It was well known that the brown planthopper (BPH), Nilaparvata lugens (Stal), contained yeast like symbiotes (YLS) in its fat body, but the mutual relationships between them have not been known well until now. It is very important to obtain and hold the apo-symbiotic BPH. On the basis of this, many techniques could be used, such as bio-determination, instrument analysis, enzyme activity measurement, to compare the differences between aposymbiotic and symbiotic BPH cultured on artificial diets, and then some nutritional matters closely related to YLS could be found, so it was possible to study the genes related to these matters. Finally, relationships between YLS and BPH could be explained on gene level. At the same time, distribution of YLS in eggs of BPH and culturing of YLS in vitro were also studied. The results were summarized as follows.1. Development of YLS in eggs of BPHContinuous paraffin slices of eggs showed the changes of YLS in BPH. The YLS ball was in the end of the eggs after female adults laid them, and the ball moved to the head of the egg, then go back to the end along with blastokinesis. The size of YLS ball was not changed in this course. But from then on, the ball began to larger and was not regular ball in the fifth day, the ball stretched around and the number of YLS increased apparently. To 6.5 days, the ball was parted to two parts of left and right in the abdomen of BPH and the number of YLS was increased continuously. After the egg hatched, YLS covered all the abdomen of first instar nymph. When the nymph developed to second instar, YLS collected to small balls in each segments of the abdomen.Electron Microscope pictures showed each YLS has an apparent cell wall, around which has another protective layer and then a kind of bubbling cells suffused all around or interspace of YLS group. Another rod-shaped organisms, like some kind of bacterium, were found near by YLS and the same bubbling cells also surrounded them. Not all YLS aggregated together, minority of YLS individuals freed from the YLS group, which indicated there was not a membrane-like frame around YLS group.2. Techniques of decreasing the number of yeast like symbiotes in BPHYeast like symbiotes in BPH could be decreased effectively by exposing young nymphs to high temperature 35℃~36℃. for three days, which was concluded by the results of different high temperature to YLS in the same instar nymphs and the same temperature to YLS in the different instar BPH. Because the number of YLS in BPH fluctuated in different season, it was necessary to change the high temperature or exposing time in order to obtain the same apo-symbiotic insects. It also found that the number of YLS had great effect on the emergence of BPH. It was estimated more than 5000-7000 symbiotes/mg fresh weight were necessary for BPH to emergence.The effect of one or two Antibiotics added in artificial complete diet D-97 to reduce the number of YLS in BPH was not so better as high temperature, but it was helpful to maintain the character of...
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