Abstract
The homoeotic aberration on the wing of a female of Orthosia angustipennis Matsumura (Noctuidae) is recorded. This example shows the forewing pattern mosaicly on the left hindwing and is also conspicuous in that this pattern is copied partly in the area between costai margin and vein M1. Hayashi (1961) pointed out that the forewing pattern is not copied in this area of hindwing due to the differences in the veins of radius and subcosta between fore and hindwings. It seems that the vein aberrant of the hindwing (the coalescence of traceae of radius and subcosta is imperfect and the short branches may be the residual parts of the coalescent radii, see fig. 4) is the result of copying the forewing pattern on the costal area in this case.
