It is nearly impossible to tell if a caterpillar is male or female; most species must be dissected to determine gender. However, the gender of butterflies and moths can be determined by coloring, markings on the wings and other characteristics. For instance, male monarch butterflies have black spots on their wings that females do not have.
Caterpillars are one of four life stages for butterflies. Butterflies lay their eggs on plants, and it takes a few weeks for them to hatch as small caterpillars. Butterflies have a strong sense of taste, which they use before laying their eggs to discern whether a plant is a suitable food source.
Caterpillars eat constantly to grow into butterflies or moths. Upon maturing, caterpillars go into cocoons, where they transform. The lifespan of adult butterflies varies by species, from a week to almost a year. Butterflies can reproduce once or more per year; the number of broods varies by the climate of the butterflies' habitat. Many butterflies migrate over long distances, but some maintain territories where they chase away other species.
The gender of moths can be determined by color or size of antennae. Additionally, gender can be determined before moths hatch by counting the number of notches on the cocoon.