An species is diurnal if it is active during daylight hours. Species that are active at night are called nocturnal. Species which are active mainly at dawn and dusk as called crepuscular.
Most butterflies are diurnal; they are active in the daytime. Most moths are nocturnal, they fly at night (although there are quite a lot of diurnal moths, for example, the Crimson-speckled Footman).