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1. It has been found that there are two species of spiders in Japan that change body colour. i.e. Leucauge subgemmea BOESENBERG et STRAND and Argyria venusta YAGINUMA. 2. Leucauge subgemmea weaves a horizontal orb-web about 30cm in diameter among bushes. The spider itself hides behind a leaf nearby and not in the centre of the web, which habit distinguishes it from other Leucauge. 3. The entire abdomen of Leucauge subgemmea shines golden-green when at rest but it changes colour and numerous scaly flecks appear when picked or shaken strongly. 4. Argyria venusta, when observed at Mt. Myogi (Gunma Prefecture), wove an irregular web on the underside of a leaf of a bush in cliff y ground and from the web hung vertical threads with insects and leaves at their ends. 5. The abdomen of Argyria venusta is of beautiful golden-yellow but when pic-ked or shaken strongly, the colour breaks up into numerous star-like flecks. This change follows the same pattern as in the case of Leucauge subgemmea. 6. The leaves and insects hanging from the Y shaped threads that form the web of Argyria venusta seem to be weights that keep it in shape. 7. The colour change in the abdomen of Leucauge subgemmea and Argyria venusta is probably due to the change in the pigment cells in the golden flecks while expanding and contracting. This change is instantaneous. 8. The flecks on Argyria venusta have been observed to contract by placing the spider in the dark and striking it with the sun's rays. 9. Argyria venusta is a new genus and species belonging to Conopisthinae. Its original description has been made by Mr. T. Yaginuma. (See page 11 in this paper.)