Abstract
The white-backed lanthoppers lose their dry body weight and lipid contents on a long distance flight. We analyzed these variables of insects caught over the East China Sea (31°N, 126°E) and from various parts of the Japanese islands in June and July 1986 and 1987, and compared their discriminant functions. Mean numbers of newly immigrated planthoppers, so defined when they showed the same levels of variables as those of the East China Sea population, were 4.2 to 4.5 out of 12 analyzed in samples from Nagasaki and elsewhere in Japan. They were always found inassociation with the synoptical frontal systems developed over the Japanese Islands. This finding was in conformity with the previously proposed migraton theory. Significantly different dry body weights and triglyceride and fatty acid contents among the East China Sea populations caught in 1986 and 1987 suggested that their emigration origins differed.
