The Grass Demon (Udaspes folus) is a small butterfly with a wingspan of about 4 to 4.8 cm. It is black with a large white spot on the upperside of the hind wing and several smaller whites spots on the forewing. The underside of its wings is mostly white with brown edges and spots. Habits The Grass Demon prefers forest edges or clearings where dappled light is present. Its black and white colouration may have evolved to take advantage of the dappled light in these areas. The pied pattern which seems prominent in the open is effectively disruptive in the shade and the butterfly is difficult to locate once it settles down. It is a bold insect and not easily disturbed. It usually flies in the shade among bushes and under trees keeping low and close to the ground. From time to time, it takes short flights, and, occasionally, much longer excursions into the open clearings. Its flight is quick and the path is very erratic making it very difficult to track when in flight. When basking it sits on the upperside of leaves of herbs or bushes with its hind wings pressed flat against the surface and its fore wings held half open at an angle above the hind wings. This butterfly also has a unique wing flashing display most often seen just after it has alighted on a leaf. It will move its hind wings down toward the leaf surface. When the hind wings are about half way down the fore wings also start moving downwards. On the upward beat both wings are moved simultaneously till the hind wings come together. Then it again begins the downward beat. Each beat is performed very slowly and the butterfly is very conspicuous during this time. This display is unique since no other peninsular Indian butterfly is known to display the capability of moving forewings and hindwings separately. The Grass Demon is a nectar lover and has a long proboscis compared to body size. This makes it easy to get to nectar of flowers with long corolla tubes. In gardens, the Common Periwinkle (Vinca rosea) and Lantana are its favourite flowers. It rarely visits bird or dung droppings. It is fond of water and often seen perched on a stone in a stream-bed.