This study was conducted to investigate specific stages and distribution of overwintering nymphs of green rice leafhopper, Nephotettix cincticeps by measuring head capsule width. The nymphal head capsule width of the 1st instar to the 5th instar was 0.381, 0.502, 0.673, 0.979 and 1.128 ㎜, respectively. Its coefficient variation was 5.3, 4.0, 3.0, 4.5 and 5.3%, respectively. Growth ratio of each instar was not significantly different among 2nd to 4th instars as 1.31 to 1.34, but for the 5th instar it decreased as 1.28. The logarithm of the nymphal head capsule width was regressed as a function of the stage number of insects, resulting in LogY = 1.4627 + 0.1192X (r² = 0.9993). Also fitness to the Dyar’s law for the nymphal head capsule width of each instar was 98% or over and the Dyar’s constant (K) was 1.316. The occurrence of N. cincticeps was maximum at the end of January with 195 individuals/0.25 ㎡. The most abundant instar in the overwintering N. cincticeps population was 4th instar accounting for over 90%. Population of the 5th instar began to increase from mid-March, and adults began to occur in early April.

Determining age distributions of insect is required for many basic ecological studies. Most of insect developmental studies, the head capsule width and other developmental traits have been widely used to distinguish the instars. Unlike to other insect species, collembolan continues to molt after they reach sexual maturity. So these traits sometimes make it difficult to conduct developmental studies. Model animal used in this study was Paranura rosea a native collembolan speciese. To determine the age groups of P. rosea, we periodically (1week) made digital images of P. rosea (over 100 different images) under the magnifier (DIMIS-M) for consecutive 20 week. And then the head capsule width and the surface area of P. rosea were analyzed using a image software (ImageJ). In this test the head capsule widths and surface area were set as developmental parameters. Both two developmental parameters showed time-dependent increase patterns. And they gave good agreements between predicted developmental parameters and observed parameters (r2=0.83 and 0.71). Based on the reproducibility of juveniles and statistical mean separation tests (tukey's test), both two developmental parameters could be divided into 3 age groups. The information given this study will be used as a basis for understanding the population dynamics and other ecological research.