Swamp Milkweed Leaf Beetle

Meet a Swamp Milkweed Leaf Beetle! 

When I saw this beetle, my first thought was that this was some sort of ladybug; aphids love eating milkweed, and ladybugs love eating aphids. Of course, I didn't see aphids on this milkweed, but I just chalked it up to a ladybug that was performing due diligence, making sure this milkweed didn't have a meal.

But apparently this is a completely different type of beetle, one that eats the milkweed plant itself. Though their most frequently used common name seems to imply they exclusively feed on Swamp Milkweed, they will actually eat most (all?) of our milkweeds, and their second most frequently used common name is actually the broader Milkweed Leaf Beetle. Though they have a different look, they're related to another eater of poisonous plants, the Dogbane Leaf Beetle.

Note the red coloring. As an eater of a poisonous plants, this beetle is trying to advertise to predators that it too is poisonous. This is known as aposematism. Milkweed plants host lots of these aposematic insects, including the Large Milkweed Bug, the Small Milkweed Bug, the Red Milkweed Beetle, and of course the Monarch butterfly. All these insects have red/orange coloring, a pretty good don't-eat-me signal.

June 5, 2021 at Duke Farms
Photo 136368090, (c) jpviolette, some rights reserved (CC BY-NC)


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