Feeding Habits and Honeydew Components of the Green Rice Leafhopper, Nephotettix cincticeps UHLER (Hemiptera : Deltocephalidae)

Abstract

Nephotettix cincticeps UHLER inserted its stylets mostly into both the vessel and sieve tube of rice plants. The frequency of honeydew excretion and honeydew components were closely related to the sucking sites in the vascular bundle tissues. The honeydews excreted frequently at the rate of 426-930 droplets per hour (or 21.3-46.5 μl/hr) contained no sugar. They seemed to be derived from the xylem sap. On the contrary, the honeydew droplets containing both sugars and amino acids were excreted less frequently, e.g., 18-113 droplets per hour (0.9-5.7 μl/hr), which seemed to be derived from the phloem sap. Percentages of sucking times on the phloem and xylem were about 70 and 30%, respectively. The total amount of honeydews excreted by a single female adult per day on rice seedlings averaged 235 μl at 25°C. Four kinds of sugars and at least two kinds of amino acids were detected in the honeydew. The total sugar and amino acid concentration in the honeydew varied widely from 0.34 to 0.95% as glucose and 0.002% or less as leucine, respectively, since the honeydews deposited consisted of two kinds of droplets originated from the xylem and phloem sap. A single adult female discharged about 1 mg of sugars and less than 4 μg of amino acids per day.