Ten days ago, I wrote about monarch butterflies returning from Mexico and flying much further north than is typical, and some of the risks they face because of that. Many of you responded with your own similar observations and stories of monarchs across the country. Since writing that post, I’ve spotted numerous monarchs both at our family prairie and in our Platte River Prairies, and reports to Journey North show monarchs have traveled even further north than we are here.
Earlier this week, my wife got to watch a monarch laying eggs on some small whorled milkweed (Asclepias verticillata) plants in our backyard prairie garden. A monarch (same one?) came by when I was around too, so I snuck out and tried to get photos of it but it was too cagey. At the end of last year, Kim and I were talking about how surprisingly fast the couple of small whorled milkweed plants we’d gotten for the garden had spread. Now we’re worried that we don’t have enough whorled milkweed to support all the eggs that have been laid on them!
A monarch egg on whorled milkweed in our backyard.
Usually, the monarch laid only a single egg per plant, but some plants had as many as three on the same small plant. Hopefully, those caterpillars will be able to make their way to surrounding plants if they overwhelm the ones they start on.
Yesterday, I went walking in our Platte River Prairies, hoping to find some eggs there as well. I was looking for common milkweed (Asclepias syriaca) but all I found was more whorled milkweed. Sure enough, I found eggs on some of those plants too, and even spotted a couple tiny caterpillars. All the plants I found were in prairie patches we’d burned and grazed last year. I’m guessing the monarchs had the same impression I did of that grazed habitat – it’s sure easier to find tiny milkweed plants when there aren’t a lot of taller plants and thatch hiding them!
This tiny little caterpillar was busily munching away on whorled milkweed in our Platte River Prairies. It was just a couple millimeters long.
Whorled milkweed doesn’t usually get the accolades or attention it deserves. In our prairies, it is often most abundant in areas where native prairies have been degraded by a long history of overgrazing and broadcast herbicide use (before we acquired the properties). The plants are relatively small (often less than a foot tall) and have small white flower clusters and skinny seed pods. When we’re harvesting seeds for our prairie restoration work, we try to get enough seed to ensure the species will establish in our plantings, but probably haven’t always worked as hard as we should at it.
Whorled milkweed is often overlooked and underappreciated, but is certainly proving its worth this spring.
The monarch eggs and caterpillars I found yesterday were in a restored prairie we’d seeded back in 2000. The patches of whorled milkweed I found were over 15 feet in diameter, and some contained well over 100 plants. I’m awfully glad now that we took the time to find and harvest whorled milkweed seeds during the summer of 1999, and wish we’d harvested even more. Nevertheless, the plants that established back in 2000 have spread successfully and are now helping to rear the next generation of monarch butterflies. When those caterpillars emerge as butterflies, they’ll find themselves in the middle of a large and diverse prairie community, full of flowers for them to feed on. Eighteen years ago, that same location was a cornfield. Today, it is giving some way-too-early monarchs a chance at survival.
This plant had both an egg and an already-hatched caterpillar. Hopefully, as it grows, it will find not only sufficient milkweed, but also abundant nectar resources for its adult life. (You can see a larger and more clear version of this image by clicking on it. Maybe you can figure out what the little white bump is on the caterpillar’s back… Part of the egg? Something else?)
The Prairie Ecologist 