Abstract:To make clear effect of yeast-like symbiotes (YLS) on the reproduction and ovarian development of the small brown planthopper (Laodelphax striatellus), the changes in the number of YLS and the correlations of YLS with the ovarian development and fecundity of L.striatellus females were studied using the haemacytometer in combination with the photomicrograph. The results showed that the number of YLS reduced along with the growth of adult females at 25℃ or treated at 35℃. After the insects were treated at 35℃ for 48h at the 4th instar, the number of YLS in adult females was significantly reduced. The insects at 25℃ or treated under 35℃, there was a negative correlation between the number of YLS and ovarian development (r=-0.903,P<0.05; r=-0.970,P<0.01), and their daily fecundity displayed a positive correlation with YLS number (r=0.725,P<0.05; r=0.659,P<0.05). It is suggested that the YLS existence in L.striatellus will be beneficial for the ovarian development and fecundity of the female adults.