Like other insects, butterflies use heat from the sun to warm up their bodies. That’s why they are more likely to rest with their wings open in the morning, when they are trying to warm up. On this tropical checkered skipper, you can also see that the body and the inner portion of the wings are dark, which also aids in absorbing heat. The veins in butterfly wings contain the insect equivalent of blood, so dark coloration around the veins or the inner portion of the wings can help them raise their body temperature.
During the heat of the day, most butterflies rest with their wings folded above their back. Because it is generally hot, many butterflies have lighter colors on the underside of their wings, which reflects sun and keeps them from overheating. And, of course, simply folding their wings above them reduces the amount of sunlight that is hitting their wings as well.
