Abstract: Utilization of sugars by females of Sogatella furcifera (Horvath)(Homoptera: Delphacidae) from rice plants of different age groups of resistant Rathu Heenati (RHT) and susceptible Taichung Native 1 (TN1) was studied by measuring honeydew excretion, sugars in the honeydew, total sugar contents in rice bleeding sap, and changes of a-glucosidaSe activity in planthopper individuals. Insect feeding decreased with the increase of plant age of both RHT and TN1 varieties. Regardless of varietal susceptibility, total sugar content in rice bleeding sap increased with increase in plant age. Analysis of honeydew by high performance liquid chromato graphy (HPLC) revealed that quantities of sucrose and fructose were significantlytess in honeydew excreted on RHT than on TNI plants, indicating that S. furcifera ingested less but utilized well the phloem sap from RHT as compared with TN1.Glucosidase activity of S. furcifera after feeding on RHT was significantly lowerthan on TN1, and was positively correlated with changes in insect body weight,There may exist two independent mechanisms which control ingestion of food, and digestion and absorption of the ingested food in S. furcifera.

Key words: Sogatella Surcifera, rice, rice bleeding sap, sugars, a-glucosidase acti- vity