To Be A Monarch Butterfly
Here you see several Monarch larvae, or caterpillars, eating milkweed. In the wild you won't find more than 1 or 2 on a plant, but in captivity the population density can become very high. They get along together quite well. Milkweed is the Monarch larva's only food. The plant's thick, glue-like sap is poisonous to most creatures. The Monarch assimilates the poisons into its own tissues, making it an unpleasant mouthful to birds and many other insect eaters.
The caterpillars of many butterflies and moths are commonly known as "worms", even though they really aren't worms at all. For example, the "cabbage worm" is actually the larva of the common white butterflies you see everywhere. The "tomato worm" and "tobacco worm" are the larvae of hawk moths, also known as sphinx moths, which are about the size of hummingbirds and hover similarly when feeding on nectar. "Apple worms" grow up to become small moths. "Corn earworms" become medium-sized moths.
Most varieties of larvae are difficult to raise in captivity. They wander away from their food plants and become lost, or they have difficulty getting along with one another. The Monarch doesn't do those things, so it is one of the easiest caterpillars to raise. The ones you see above aren't in any kind of cage or box; they're on plants that sit openly in a vase on a table.
One female butterfly may lay as many as 500 tiny eggs, one at a time, on the leaves of various milkweed plants. In the wild, the number that survive to become butterflies can be counted on your fingers. Spiders and other predators consume the eggs and young larvae. Parasitic flies lay eggs on larger larvae; their maggots consume the larva from the inside out, usually waiting until after it has become a chrysalis before they bore their way out. People who have the larvae's favorite food growing nearby may find chrysalises on their eaves, gutters, fences, and garden plants; not realizing what these are, they destroy them.
By bringing them indoors, we shield them from their predators, increasing the survival rate to over 90%. This is achieved by collecting them as eggs and raising them indoors throughout their larval and pupal stages. It takes an experienced eye to readily discern a creamy yellowish-white Monarch egg on the underside of a milkweed leaf. Other objects of similar color and size may be found there, but upon close examination with a magnifying glass the Monarch egg is found to be exquisitely beautiful. It is not perfectly round, but is drawn up to a narrow tip on the end away from the leaf's surface. It is not smooth, but is faceted with several rows of indentations, radiating out from the tip and down the sides.
About three days after it is laid, the egg darkens, becoming gray on the sides and black at the tip. The caterpillar's skin has formed and is showing through the translucent shell. Soon it chews its way out, turns around to devour the rest of the shell, and then wanders a short distance away to begin munching milkweed leaves.