By Reba Kocher

Listen to this blog post here:Milkweed_Bugs.mp3

If you have been keeping up with our blog posts, you know how much we love milkweed. We have a lot of it planted in our pollinator garden, and there are some stalks found near the childrens’ garden. If you have visited, or if you have milkweed growing at your home, you may have noticed a ton of orangish-red and black bugs crawling all over the plants. No need to fear! They are completely harmless to you and to other milkweed lovers--like monarch caterpillars.

These little guys, called Lesser Milkweed Bugs (Lygaeus kalmii) and Large Milkweed Bugs (Oncopetus fasciatus), look very similar to each other. They are differentiated by size and the design on their backs. Lesser Milkweed Bugs have black heads and a triangle on their backs that connects to their membranous wing portion (the tip of their back). In contrast, the Large Milkweed Bugs have red heads, a diamond on their backs, and a horizontal line before their membranous wing portion. Another thing that sets them apart is migration. The Large Milkweed Bugs migrate south at the end of their season (around fall) while the Lesser Milkweed Bugs remain in Ohio. The Lesser Milkweed bugs will lay their eggs and overwinter.

An adult Lesser Milkweed Bug. Photo by Joe Boggs.

An adult Large Milkweed Bug. Photo by Joe Boggs.

They are both considered true bugs. This means that they have a sucking mouth parts, called a proboscis, that injects a digestive enzymes into the plant so they can then suck up the liquified plant matter. Learn more about true bugs here: https://askabiologist.asu.edu/explore/true-bugs . These milkweed bugs both feed on common milkweed (Asclepias syriaca), but they can also feed on other Apocynacae, like butterfly milkweed. They tend to only eat the seed pods and seeds. Due to the length of their proboscis, they can only reach up to the outside layer of the seeds inside a pod. Because they only eat the seeds, other bugs, like monarch caterpillars, are able to share the same plant. Milkweed sap, which they consume through the seed pods, contains a toxin called cardiac glycosides. Interestingly, their aposomatic coloring acts as a warning sign to predators that they are harmful, and all milkweed herbivores show red/orange on black coloration. In addition to this, studies have shown that predators that eat milkweed bugs have often fallen ill or even died from consuming these bugs. Luckily for us, we do not go around eating milkweed bugs! They are also not a pest, so they do not really need control methods. These are just two little bugs living their best lives.