When will the Monarch’s be back and laying eggs?

monarch on flowers

One of the most frequent questions we get at the Nature Center is “When will we see Monarchs again?” Today, we will answer that question in the classic nature fashion of guesstimates.

When monarchs migrate to Mexico in the fall, the butterflies that make it are a super generation that will live up to eight months. On the way back, they will go through as many as four to five generations to make it back to Canada.

The journey will begin in March when the monarchs leave Mexico. It will take five to seven weeks for the monarchs to get back to Canada. Once the first generation of monarchs has left Mexico, they fly a few hundred miles north to find a patch of milkweed, lay eggs and then repeat the process over again. This is how they will make it through up to five generations.

This is also why milkweed along the migration routes is so important. On the way down, they’re pit stops but, on the way back, they’re important for laying eggs. They are important for the new generations to keep moving back toward Canada.

There is a really cool resource on the Journey North website that tracks the migration of monarchs, among other migratory animals. They are able to track the monarch migration due to citizen scientists who report their first sightings of things like monarch adults, monarch eggs and milkweed growth.

According to the 2021 spring migration map, adult monarchs have been seen from Mexico to central Iowa. This from January through May 23. It’s probably a safe guess to say in the next two or three weeks, we should be seeing adult monarchs in our area. Shortly after seeing adult monarchs and milkweed, we should start seeing monarch eggs.

Monarchs lay their eggs on the underside of milkweed leaves, possibly on the stem and maybe on the underside of the blooms as well. If you’re looking for them, you’ll have to look hard as they are almost small enough to pass through the eye of a needle. They are also a bit delicate and when looking for them, you should be careful moving the leaves so the eggs don’t fall off.

Once you find eggs, as long as the milkweed plant is fairly undisturbed, you should see caterpillars in the next 8 to 10 days. The monarch caterpillar will be in the egg stage for three to eight days but they are very tiny once they hatch from the eggs.

They will eat the milkweed leaves and grow almost 2,000 times their size. It will be easy to tell if there is a caterpillar on the milkweed because there will be holes in the leaves and other leaves will have dark spots on them that are actually caterpillar droppings.

If you find all these signs, of monarch caterpillars, it shouldn’t be too long before you’re seeing a lot of monarch butterflies around. If you find monarch eggs or caterpillars or even finally see that first adult monarch of the season, share it with us! We would love to know so we can keep a lookout for ourselves!


Here are the resources we used:

Journey North

National Geographic article about Monarch Migration

Save Our Monarchs: How to Find Monarch Eggs and Caterpillars