Butterfly Metamorphosis as a Natural Clock

By Frank Leibfarth

The average lifecycle for a monarch butterfly last approximately 6-8 weeks. The metamorphosis, or maturation, of the monarch from an egg to an adult butterfly goes through four distinct stages within the 6-8 week cycle; therefore, the metamorphosis can be viewed as somewhat of a "natural clock," or a natural phenomenon which defines a measurable period of time.

butterfly eggThe "natural clock" of the monarch butterfly will start when a full grown monarch first lays its egg. The egg is only a few millimeters in diameter and is always laid on the leaf of a milkweed plant. During the spring and summer, the egg stage only lasts 3-4 days; thus, an observer can determine that a small egg on a milkweed plant must be only the very beginning of a monarch's lifecycle.

caterpillarAfter emerging from its egg, a monarch caterpillar eats milkweed leaves for approximately two weeks. As the caterpillar grows, however, it sheds 5 different layers of skin. Connecting the caterpillars lifespan to a natural clock, one can determine that the monarch is anywhere from 4-18 days old when in the caterpillar stage and can further determine an approximate age for the caterpillar because of the caterpillars size. Also, if one could be in constant observation of the caterpillar, the times at which the caterpillar sheds each of its skins could break down the two-week period of the caterpillar's maturation into even smaller increments.

chrysalisThe third stage of a monarch's lifecycle is the chrysalis, or pupa, stage. The chrysalis stage begins about 2 weeks after the caterpillar hatches from its egg, or about 18 days from the time when the monarch egg is laid. The chrysalis stage lasts 10 days from the time the caterpillar spins its cocoon until the time the full grown butterfly emerges. An observer can even determine how long the chrysalis stage has progressed simply by the color of the cocoon, which begins green and progresses through brown to yellow to orange.

butterflyThe forth and final stage of the monarch's lifecycle is the butterfly stage. A fully grown monarch usually emerges from its cocoon in the 28th day of its lifecycle. A fully grown monarch butterfly usually lives 2-6 weeks. Its primary objective in its short lifespan is to mate and lay eggs so that the next generation of monarchs can begin their lifecycle.

The metamorphosis of a monarch butterfly can be successfully used as a natural clock because of the stages of its lifecycle that occur at predictable times. The clock can successfully frame about a month and, since the monarch species has four generations of maturation per year, the clock can frame up to four month-long cycles per year. Unfortunately, the times at which monarchs lay their eggs are variable because of the longer lifespan of the butterfly stage. The clock is somewhat limited, therefore, because it can only frame the one month period of metamorphosis. The largest limitation associated with using the monarch butterfly as a natural clock, however, is the irregularities that the forth generation exhibits. The fourth generation adults actually live 6-8 months and migrate to northern-Mexico for the winter. The adult monarchs migrate back north in the winter, mate, and lay new eggs in order for the first generation of the new year to begin.

  Stage Length Age of Monarch
Egg Stage 3-4 Days 3-4 Days
Caterpillar Stage 14 Days 17-18 Days
Chrysalis Stage 10 Days 27-28 Days
Butterfly Stage 14-42 Days 28+ Days