Butterflies are insects that belong to an order named Lepidoptera, which includes moths too. Even though butterflies belong to the "insect" category, they are significantly different from other insects. All insects have three main divisions to their bodies: head, thorax, and abdomen. Insects have their skeleton on the bodies, not inside them, like the mammals.
 
Structurally, butterflies are like all other insects, but their most important difference is the scale covering on wings and body. Unlike other insects, they also have the ability to coil up their feeding tube, or proboscis. All insects have six legs attached to the thorax, although some butterflies have shortened front legs. The world’s most abundant creatures are the insects, whose known species outnumber all other animals and the plants combined.