Milkweed Cosmos

| Learning

Milkweed cosmos: A colony of milkweed is almost its own world.  Most of us have planted milkweed to attract and support the Monarch butterfly, but eventually the other insects that are dependent on it find our milkweed patches.  

On the one hand, these bugs are just doing what they’re supposed to be doing–living off of milkweed. They are fulfilling their ecological roles. This relationship is a great example of how insects can keep the population of a plant in check. The three main insects (besides aphids) that rely upon milkweed and can cause varying levels of damage or interest depending on your perspective are Milkweed Bugs (there are two separate species Large and Small), Milkweed Beetles (Red Milkweed Borers), and Swamp Milkweed Leaf Beetles. You can follow the links to learn more about each one. 

Milkweed beetle on Rose Milkweed
Milkweed beetle on Rose Milkweed; Milkweed bug to the left.

The Milkweed Bugs eat the seeds of the milkweed plant, frustrating for those trying to collect seeds to propagate milkweed, or they’re helpful if you don’t want your plants sending out too many seeds. 

 The Milkweed Beetles lay eggs on the lower stems, near the base of the plant. Their larvae then consume the milkweed roots, which could potentially weaken or kill a milkweed plant, so this possibility can make them unwelcome residents or beneficial since they can help keep a plant like Common Milkweed in check. They do an

amazing squeak if you pick them up, and they reportedly make a purring sound when happy. Yes, these insects are communicating emotions. Read more here: Red Milkweed Beetles

Swamp Milkweed Leaf Beetle

Our last beetle is the Swamp Milkweed Leaf Beetle. They feed on the foliage, possibly impacting whether a female Monarch would decide not to lay her eggs on the milkweed. Theoretically, she would detect that the leaf is damaged/unhealthy and not fit for her eggs. Another concern is that while the beetles are chewing a leaf, they could incidentally consume a Monarch egg.  

How do you feel about the insects besides the Monarch that rely upon milkweed? Are you encountering a lot of Milkweed Bugs? Milkweed Beetles? What’s your approach?  Control them  or let nature take its course? We didn’t discuss Milkweed Tussock Moths. Have you seen those? 


Photos & text: S. Walquist