The Spring Monarch Migration is Underway!

April 03, 2018

The Spring Monarch Migration is Underway!

With the warmer temperatures, monarch butterflies have started migrating north from Mexico, where they have spent the winter.  Over the next several months, they will fly as far as the northern United States and southern Canada, where they will spend the summer before returning to Mexico in the fall.

Despite increased monarch conservation efforts across North America, monarchs are still in trouble. Since the 1990s, more than 90% of their population has been lost.  This is in large part due to habitat loss, both in the United States and in Mexico.  This year, the monarch population suffered another unfortunate loss, with a 14% decline from 2016-2017 numbers.  Population estimates are measured by the total forest area in Mexico occupied by overwintering monarchs.

Here’s how you can help:

Plant milkweed: The most essential plant for monarchs is milkweed: the only plant female butterflies lay their eggs on and the only plant the caterpillars eat. Without milkweed, we will not have monarchs.

Add nectar-producing plants with a variety of bloom times to your garden: Since monarchs migrate through the St. Louis area in both spring and fall, it is important that they have a food source for both legs of their journey.  For the fall migration, we recommend using varieties of aster and goldenrod.

Avoid using pesticides & insecticides in your garden: Pesticides are not selective, so spraying for one type of insect can have adverse effects on all of them, including monarchs and beneficial pollinators.  When purchasing plants for your garden, make sure the plants have not been pre-treated with insecticides like neonicotinoids.

Report your sightings: Citizen Science can help inform researchers of migratory patterns and population boosts or declines.  Reporting your sightings of all stages of the monarch life cycle to organizations like Journey North is a fun way to engage with citizen science programs while also contributing to larger research efforts.  Here’s what to look for:

• Eggs: Look under milkweed leaves to find monarch eggs. These eggs are only about the size of a pinhead, so look closely!
• Caterpillars: Caterpillars will almost always be found on milkweed plants. They may be different sizes, ranging from two millimeters to almost two inches.  These sizes indicate different stages of the caterpillar’s life, called instars.
• Chrysalises: Small green chrysalises can be found on milkweed or on other plants. They can sometimes even be found on window sills or the siding of houses!
• Butterflies: Most people can easily recognize the iconic orange and black monarch butterflies. If you look closely, you can determine whether the butterfly is a male or female.  Male monarchs have small black scent spots on their hind wings, which help them attract female butterflies.  Females don’t have these spots but have wider black veins on their wings.