Abstract
The sexual dimorphism in the nymphal stages of Tingidae was observed by means of a scanning electron microscope on the basis of 9 Japanese species. The following morphological differences between male and female nymphs are externally recognizable on the 8th and 9th sternites of the 4th (excepting Cysteochila fieberi observed only on the 5th instar nymphs) and 5th instar nymphs of each species. In the female, the hind margin of the 8th sternite is distinctly projected posteriorly forming an arched sclerite. The lateral sides of the convexity of the 9th sternite are straight and convergent posteriorly, so as to form a V-shaped sclerite. A series of very minute holes are arranged in a row along the median line of the 9th sternite. The 9th sternite of the 5th instar nymph is provided with a small bifurcate (W-shaped) projection on its postero-central margin. In the male, the hind margin of the 8th sternite is not projected posteriorly. The converged lateral sides of the convexity of the 9th sternite are outwardly curved, so that it forms a U-shaped sclerite. The 9th sternite is provided with a minute hole near the posterior end of its median line, and with three to eleven minute processes around the minute hole.
