The Milkweed Community

Adult monarch butterfly on common milkweed © Beatriz Moisset

Adult monarch butterfly on common milkweed
© Beatriz Moisset

The monarch season is coming, and gardeners throughout the country are getting ready to welcome them with milkweeds lovingly cultivated in their gardens. They also brace themselves to battle whatever ills may affect the caterpillars. Milkweed bugs and milkweed beetles are seen with hostility. The “dreaded” tachinid flies, and “hated” stink bugs infuriate gardeners even more. Aphids are not welcome. Lady beetles and lacewings generate mixed feelings because they feed on aphids but they are not loath to snack on some monarch eggs or small caterpillars.

It is important to take a look at entire ecosystems, not just single species as Carole says in “Saving the Monarch Butterfly.

“The Monarch Butterfly is in deep trouble, and many passionate organizations have been created to save this single species. But a focus on protecting habitat instead of concentrating on a single species will provide lasting benefits for all species of wildlife and the native plant communities that support them, a far more worthy effort to many environmentalists and wildlife gardeners.”

Lonhorned milkweed beetles on cmmon milkweed © Beatriz Moisset

Longhorned milkweed beetles on common milkweed
© Beatriz Moisset

So, let us take a quick look at some members of the milkweed community. Despite the formidable defenses these plants have, many species have coevolved with them and can use them as food. They incorporate the milkweed toxins and use them to deter their enemies. In turn, many predators have also coevolved and can eat the milkweed eaters. An entire food chain has developed this way.

Milkweed tussock moth caterpillar © Beatriz Moisset

Milkweed tussock moth caterpillar
© Beatriz Moisset

Most monarch lovers are familiar with the brightly colored milkweed bugs and milkweed longhorn beetles. Bear in mind that these insects are represented by a fairly large number of species. That is, there are more than just one milkweed bug and one milkweed beetle. A few other beetles also feed on milkweeds, and several moths also do so, among them the tussock moth and the delicate cycnia.

Laarge milkweed bug, Oncopeltus fasciatus © Beatriz Moisset

Large milkweed bug, Oncopeltus fasciatus
© Beatriz Moisset

Sooner or later, those who raise monarch caterpillars are bound to meet two insects which will make them unhappy; one is a predator, the spined soldier bug, the other a parasite, the tachinid fly, Lespesia.

Spined soldier bug, Podisus maculiventris on goldenrod © Beatriz Moisset

Spined soldier bug, Podisus maculiventris on goldenrod
© Beatriz Moisset

Juvenile (nymph Podisus maculiventris feeding on dogbane caterpillars. These caterpillars cause serious damage to dogbanes © Beatriz Moisset

Juvenile (nymph) Podisus maculiventris feeding on dogbane caterpillars. These caterpillars cause serious damage to dogbanes
© Beatriz Moisset

The spined soldier bug, Podisus maculiventris, is a good hunter of caterpillars and beetle grubs. It has a sharp beak with which it impales its victims. It injects some saliva which turns the inside of the prey into a smoothie and proceeds to drink this nutritious cocktail. The sight of a shriveled monarch caterpillar hanging from the beak of a stink bug causes great distress to the gardener.

Tachinid fly, Lespesia. © Stephen Luk

Tachinid fly, Lespesia. This specimen parasitized an Eastern tent caterpillar
© Stephen Luk

Lespesia's puparium and the Eastern tent caterpillar cocoon from which it emerged © Stephen Luk

Lespesia‘s puparium and the Eastern tent caterpillar cocoon from which it emerged
© Stephen Luk

The tachinid fly mentioned above goes by the name of Lespesia. It lays its eggs on caterpillars of a large number of species. The tiny fly larva digs inside and proceeds to eat its victim until it reaches full size. Then it comes out of the dying caterpillar and dribbles a sticky trail until it drops to the ground. Not a pretty sight.

Although these two insects kill some monarchs, we should not hate them. Actually, their diet is so diverse that it includes a number of pests. They are both used as pest controls for this reason and even sold for this purpose. Podisus is known to eat Mexican bean beetles, European corn borers, diamondback moths, corn earworms, beet armyworms, fall armyworms, cabbage loopers, imported cabbageworms, Colorado potato beetles, and velvetbean caterpillars. The tachinid fly is reported to feed on tent caterpillars, armyworms, cutworms and corn earworms.

Nature is far more complicated than it appears at first sight. It may seem paradoxical, but the spined soldier beetle and the Lespesia fly are indirectly the friends of monarchs, because they help cut down on pesticides. Moreover, we must remember that they have coexisted with monarchs for eons without driving them to extinction. The same can be said about the milkweed herbivores –beetles, bugs and moths. They haven’t driven milkweeds to extinction and they are not likely to do so. We are the ones that pose a threat to milkweeds and to monarch butterflies with our pesticides, habitat destruction and introduction of invasive species.

Let saving the pretty butterfly be the portal to saving the entire community, all the creatures that creep and crawl, the ones that jump or fly and even the ones that kill or get killed. Let us embrace the web of life in its totality, with all its beauty and ugliness.

Delicate Cycnia. Another member of the milkweed community © Beatriz Moisset

Delicate Cycnia. Another member of the milkweed community
© Beatriz Moisset

Additional readings
You may find this Flickr group interesting: The Milkweed Zoo
More members of the milkweed community
The monarch butterfly as part of the food web: Monarchs and their Enemies

© 2015, Beatriz Moisset. All rights reserved. This article is the property of Native Plants and Wildlife Gardens. We have received many requests to reprint our work. Our policy is that you are free to use a short excerpt which must give proper credit to the author, and must include a link back to the original post on our site. Please use the contact form above if you have any questions.

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  1. Mona Miller says

    Just found a new milkweed research group called Milkweed Watch. They are at the University of Nebraska. They are asking people to help them document the diversity of milkweed plants and the species that use milkweeds.

  2. says

    I really love this piece, revealing and sharing the milkweed community in all its complexity. With more and more gardeners becoming aware of the importance of milkweeds in their gardens, I hope your words can pacify them a bit when “the balance” inherent in a natural community does a little balancing in their garden. As gardeners, sometimes our protective instincts do more harm than good.
    Cynthia Abbott, aka Gaia gardener recently posted..Maintenance in the Native Plant Garden: Springtime Editing, Part 1

    • says

      Thanks. It is true that some people lose their sense of perspective. They are so intent on saving the iconic butterfly that they forget about saving the entire habitat. They also fail to appreciate the “ugly” or the somewhat obscure species that are part of the milkweed community. We need to accept Nature in its totality. I am always pleased to meet those with a clearer understanding of ecological interactions.
      Beatriz Moisset recently posted..The Earliest Pollinators: Beetles and Flies

  3. says

    Beatriz, thank you for this great post about the entire Milkweed community. Too often, after a program, I am asked, “But, what is it good for? (it, referring to a Milkweed Tussock Moth caterpillar, for example)” I’m left speechless after such a question, and my cold, hard answer probably isn’t helpful, “What are we good for?” Thank you for showcasing the big picture!
    Pat Sutton recently posted..Native Plants for Sale at 5 South Jersey Ace Hardware Stores

    • says

      Every creature plays a role, big or small, in the web of life. Each time we lose one of them the biodiversity is reduced and the world is poorer for it. We don’t know what most species do, largely because that knowledge requires lots of research, that is lots of time and money. This is why we know more about pests than anything else. The species that quietly work behind the scenes go unnoticed. It wasn’t long ago that the general public knew nothing about pollinators. Nowadays, most people know nothing about mycorrhizae. A few have some inklings about biological pest controls. And so on.

      Insects are at the base of the food chain, and thus they are important. Toxic or not, some predators eat tussock moths. Perhaps some of these predators play some important role. Or, perhaps, this moth’s caterpillars keep milkweed and dogbane populations from exploding. If we really wanted to know, we would have to spend far more money on research. In the meantime, we can say very little. I share your frustration.
      Beatriz Moisset recently posted..This Way to the Restaurant.

  4. robert beh says

    We have a storm retention pond. We want to plant native plants around it, and we are considering milkweed. We do not have funds for this project. Do you know of a source for free (or very cheap) milkweed plants? We are in southern New Jersey.

    Thank you for your help.

    Robert Beh

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