Monarch Caterpillars!

What a surprise this morning, monarch caterpillars! And they are an inch and a half long.

We've been seeing an adult monarch butterfly (Danaus plexippus) a couple of times a week. The last few years we have been growing native narrow-leaved milkweed (Asclepias fascicularis) and the introduced tropical species (Asclepias curassavica) that is readily available at garden stores.

We've had little caterpillars in the past, but they seemed to get eaten by either a bird or a predatory insect. This is the first time that we have had caterpillars reach this size in years.

The group of monarch butterflies that live in California (west of the Rocky Mountains) do not migrate to Mexico with the main population from the southern Central and Eastern part of the U.S. This Pacific population overwinters along the coast in Southern California down into Baja. 

Loss of milkweed habitat has caused declines in this population. Most butterfly species lay eggs on a specific plant species and their caterpillars are dependent on that plant for food. Native milkweed can be a challenge to grow. I didn't realize that narrow-leaved milkweed dies back each winter. I thought I had killed it and took it out. Now I understand that it will grow back in the spring. Until my native milkweed is established, I supplement with the tropical species in a planter, to avoid it becoming invasive.

These hot days, with temperatures above 100 degrees are a challenge for plants and wildlife. I hope that our caterpillars make it to chrysalis. It would be great to contribute to a new generation of monarch butterflies.

Other caterpillars you might see in your CA yard

Backyard Butterfly Quiz

Mourning Cloak Butterfly

Monarchs and Jerusalem Crickets