1. Freshly emerged imagines of Papilio demoleus kept in a large cage, were offered some circular patterns of different sizes and different degrees of contour, cut out of coloured papers of the standardized Ostwald series. 2. On the coloured patterns, these hungry insects showed a characteristic feeding response: each one approached a pattern in flight, landed on it and unrolled its tongue with which it performed probing and sucking movements on the paper. Such responses on each of the patterns were counted separately. 3. The results clearly show that this insect can distinguish between forms of different sizes, and between forms presenting different degrees of contour. 4. The attractiveness to this insect in the feeding state increases with size of the form and with its compactness. 5. A definite interaction between form preference and colour preference has been established. The tendency of preferring a bigger form to a smaller one and that of preferring a compact form (poor in contour) to a broken one (rich in contour) increases with less and less attractive colours and vice versa. 6. Some experiments have brought out clearly the striking difference in the preference of the degree of contour shown by this insect (a Papilionid) and the Vanessids (ILSE, 1932). They have further provided an experimental proof for the conclusion reached by LEPPIK (1953) on the basis of his field observations that Lepidoptera prefer compact flowers for feeding.