Becoming a Monarch Butterfly

A few weeks ago here at Grand Canyon National Park, we saw our first monarch butterfly eggs which then became larvae just two days later. That morning, I had been out with my supervisor, Lonnie, as we were walking around the park to identify species of milkweed. Here at Grand Canyon on the South Rim, we have 3 common types of milkweed: Asclepias asperula (Antelope Horns), Asclepias subverticillata (Horsetail Milkweed), Asclepias latifolia (Broadleaf Milkweed).

Antelope Horns Milkweed Wildflower Stock Photo - Download Image Now - iStock

This is a picture of Asclepias asperula (Antelope Horns Milkweed).

ASCLEPIAS latifolia Broadleaf Milkweed – MySeedsCo

This is a picture of Asclepias latifolia (Broadleaf Milkweed).

Milkweeds in Arizona — Spadefoot Nursery

This is a picture of Asclepias subverticillata (Horsetail Milkweed).


The most abundant type of milkweed found around the South Rim is horsetail milkweed, you can potentially find groups of them on the side of roads and trails around South Rim. We were on the hunt for a specific type of milkweed called Asclepias asperula otherwise known by its common name antelope horns or spider milkweed. They’re harder to find with the main reason being they get eaten. We have a wide variety of wildlife here at Grand Canyon National Park like mule deer, desert big horn sheep, coyotes, elk, gray fox, and a variety of rodents and birds. Elk are to blame for eating the antelope horns. They are the largest member of the deer family and are non-native to Grand Canyon. Because of this, they are dependent on human resources and can get very comfortable around people which can potentially be dangerous.

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Monarch Butterfly Life Cycle infographic from Kids Growing Strong.

On South Rim, one of the favorite foods for elk are antelope horns, so it can be very hard to find at times, because it will have already been eaten or it will be slowly sprouting back. Lonnie took me to a few locations where he had seen antelope horns before, so that I could become oriented with what that type of milkweed looks like and its characteristics. One of the locations we had been observing was a population of around 23 antelope horns. I started to take closer looks at the plants, inspecting them for eggs or larvae. As I was inspecting the underside of the leaves, I spotted 2 eggs on 2 different plants in that population. It’s always a joy to spot eggs in hopes that you can be lucky enough to witness them hatch. The monarch butterfly life cycle is a pretty fascinating process, that I will explain more about with the help of an infographic. Monarchs go through 4 stages in their life. They first start off as an egg, they then will hatch into larvae and go through the five instar stages. Then they enter their pupation stage where they hang in a “J” shaped form which will then allow them to form their chrysalis. The monarch butterfly will hatch 2 weeks later. It’s very rare to see a the full process of one caterpillar from egg to butterfly, but I have had the opportunity of witnessing that with my mom when we started  pollinator/milkweed gardens in our backyard. It still blows my mind how quickly or slowly the process can happen and how different it can be each time. Another interesting fact about monarch butterflies is that there are 4 generations of monarchs. Generations 1-3 usually stay up north but can sometimes stay down in the southern states as well. Generation 4 of the monarch is the one that will make the migration journey to Mexico or Southern California. Here at the Grand Canyon, we are most likely seeing 3rd generation butterflies and the 4th generation butterflies being born. But, I want to point out that these caterpillars that we found on these leaves had just hatched and when they hatch, these caterpillars are so small, you can barely see them with your eyes unless you get down on ground level and get really close. When these caterpillars hatch they can measure less than 1/10″.


For scale this is what a Monarch Butterfly Egg looks like, a small cream cone shape on the underside of milkweed leaves.

This is for reference on how small and tiny Monarch caterpillars really are. This is a zoomed in picture.


That’s incredibly small! I have two pictures, one of a close up of one of the caterpillars that hatched and another picture of what monarch butterfly eggs look like. Small, right? I hope to follow these caterpillars throughout their entire life cycle, but it is unlikely since they tend to move around a lot to look for food. However, I am exciting to continue to find more here at South Rim, and who knows, maybe my next blog post will be about monarchs hatching from their chrysalis.

Until next time.

Your friend,

Cassandra Cavezza

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