Curious Monarch Biology

Help us help monarchs

How do monarchs smell, taste, and hear?

Monarchs smell with their antennae and taste with their feet. Hearing is very different with monarchs. They certainly do not hear sound as we do. They respond to air vibrations and hear ultrasound.
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How many eggs can one monarch lay?

During her lifespan, a female Monarch may lay hundreds of eggs. She deposits pin-head sized eggs on the underside of milkweed leaves, where they will hatch in 4-5 days, depending on the temperature. The newly hatched larva feeds voraciously on the milkweed, accumulating bitter chemicals from the host plant which help protect the Monarch from birds. Over the next few weeks, the caterpillar grows from 1/16th of an inch to about 2 inches in length, increasing its weight by a factor of 2,700. To accommodate this rapid growth, the caterpillar must shed its distinctively striped skin several times before it is ready for the next stage of its development; a chrysalis.

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The truth about milkweed.

The only plant a monarch can lay eggs on is a milkweed. Planting milkweed and nectar plants are both great ways to support healthy monarch populations. Our Museum recommends planting milkweed over one mile from monarch overwintering habitats which includes all inland valley areas. This encourages monarchs to begin their migration to lay their eggs. Nectar plants support the migrations to and from overwintering sites and should be planted everywhere.

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What's the difference between a chrysalis and a cocoon?

Different California Butterfly Pupae

Different California Butterfly Pupae

A caterpillar sheds its skin many times to grow. A chrysalis is the final hardening of the caterpillar's outer skin before it begins to change into a butterfly. Moths spin cocoons around their chrysalis for added protection during metamorphosis. Butterflies do not. Instead you see the beautiful exposed chrysalis until the butterfly emerges as an adult. Every butterfly chrysalis is distinctly different in appearance.

The fully-grown monarch caterpillar usually leaves the milkweed to seek out a bare branch or similar sturdy surface. It attaches itself by spinning a silk button from which it hangs upside down in the shape of the letter "j". After settling down, the caterpillar sheds its skin a final time, revealing a beautiful green chrysalis decorated with delicate gold spots. Inside the chrysalis, the caterpillar's body is undergoing metamorphosis, the process by which its tissues and organs rearrange into the startling different body of a Monarch butterfly. After two weeks, the chrysalis becomes transparent, signaling that the black and orange butterfly within is ready to emerge.

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What's the first thing that a monarch does when it emerges from its chrysalis?

When ready, the monarch chrysalis splits open along several joints, and the Monarch butterfly carefully emerges. Its wings are still folded and crumpled from confinement in the chrysalis, so the butterfly must pump fluid from its body into the wings, expanding them quickly to full size. The monarch must also assemble its proboscis, a straw-like tongue by which the monarch drinks nectar, which is in two pieces when it first emerges from the chrysalis. A female monarch has approximately 6 weeks to seek out nectar, mate, and lay eggs before she dies.
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