During my slog through Hades last Thursday, I found a group of native false milkweed bugs (Lygaeus turcicus, family Lygaeidae) frolicking on their favorite host, false sunflowers (Heliopsis helianthoides, family Asteraceae). At the time, I didn’t give much thought to the absurdity of those common names because I was too busy thinking about my poor life choice.
I understand the intent of placing “false” in front of a name because it alerts us to the risk of being fooled. The name “false boneset” (Brickellia eupatorioides) warns us that we should look closely before identifying a plant as being true boneset (Eupatorium perfoliatum). Even the prefix “eupator” in the specific epithet of false boneset references true boneset.
However, the scheme holds an air of false advertising because we’re inconsistent. A toad looks like a frog, but we don’t call toads “false frogs,” or crocodiles “false alligators,” or viceroy butterflies “false monarchs.” The next time you see a Hyundai Santa Fe, tell the owner that you like their “False Land Rover Defender.” No, don’t do that.
False milkweed bugs carry the false name because they look like small milkweed bugs (L. kalmii), which are so named because they look like large milkweed bugs (Oncopeltus fasciatus), but they’re smaller. All three bugs belong to the seed bug family, Lygaeidae. The true milkweed bugs feed on the seedpods and seeds, both developing and mature, of milkweeds (Asclepias spp.) as well as a few other members of the dogbane family, Apocynaceae.
Like other insects that focus on milkweeds, the large and small milkweed bugs extract the essence of milkweed seed for both nutritional and defense purposes. We’re all familiar with the monarch butterfly (Danaus plexippus) story.
Monarch caterpillars sequester and repurpose toxic cardenolides found in milkweed sap to serve as protection against predators. The protection extends to the adult butterflies. The milkweed bugs do the same thing, as advertised by the orange and black warning (aposematic) colors.
The aposematic color motif is shared with other milkweed-feeding insects that sequester cardenolides. It’s an example of Mullerian mimicry where two or more toxic species share features that send a “don’t eat me” message to predators.
False milkweed bugs do not feed on milkweed seed. They prefer to feed on the developing and mature seeds of false sunflowers, which became false when plant taxonomists split them from true sunflowers (Helianthus spp.).
False sunflowers are also called eastern ox-eye, ox-eye, oxeye sunflower, and smooth oxeye. Since the bugs have nothing to do with milkweeds, a more truthful common name would be “ox-eye bugs.” On the other hand, that name may imply the bugs have huge ox-like eyes (?).
However, we shouldn’t jettison the name “false milkweed bugs” too quickly because it references a hidden truth. False milkweed bugs belong to the same genus as small milkweed bugs. They’re shaped like milkweed bugs, and they share the same aposematic coloration, but they don’t feed on milkweeds to acquire toxic cardenolides.
It was once speculated that false milkweed bugs are like viceroy butterflies (Limenitis archippus), which lack chemical defenses but mimic chemically protected monarch butterflies to fool predators. When a non-toxic species mimics a toxic species to escape predation, it’s called Batesian mimicry.
Up until the early 1980s, the true plant host of the false milkweed bugs was open to debate. The mystery was solved in a paper published in 1983, with the author reporting that false milkweed bugs prefer to feed on the seeds of false sunflowers over the seeds of milkweeds [cue Handel’s “Hallelujah Chorus”].
The plot thickens with a paper published earlier this year. The authors reported that the seeds of false sunflower produce cardenolides. It’s only the second report of these defense toxins, which are most strongly associated with plants belonging to the Apocynaceae, being found in a plant belonging to the Asteraceae family [cue the Rolling Stones’ “Surprise, Surprise”].
The authors further disclosed that if small milkweed bugs were forced to feed on milkweed and false sunflower seeds, the bugs were equally good at sequestering the cardenolide toxins extracted from both types of seed. However, if the same test was conducted on false milkweed bugs, the bugs were better at sequestering the toxins from false sunflower seed compared to milkweed seed.
The authors concluded that small milkweed bugs and false milkweed bugs shared a common ancestor. However, the availability of cardenolide toxins in both false sunflower and milkweed seeds supported a divergence, so the false milkweed bugs don’t need to compete with other members of the Lygaeidae family that feed on milkweeds.
The bottom line is that the reason false milkweed bugs and large and small milkweed bugs resemble one another isn’t Batesian mimicry; it’s Mullerian mimicry. They are all protected by sequestered cardenolide toxins, but from different plant sources. If it’s the thought that counts, perhaps the name “false milkweed bug” fits after all.
On a side note, a few years ago, I photographed a large milkweed bug sucking the juices out of one of its pack mates. I don’t know if the victim was dead before the injustice or if the aggressor killed it. Or, if I were witnessing the beginning of a zombie bug apocalypse. Regardless, it would seem that the bugs aren’t strictly vegetarian.
Bugs: True or False
Although taxonomy can be taxing, it can help identify insects. Insects are primarily separated by taxonomic Order. Plants are most commonly separated along Family lines.
It’s particularly helpful when the name of the insect's taxonomic order describes its members. The suffix “-ptera” is derived from the Greek pteron, which means “wing.”
“Coleo” is derived from the Greek word koleos, which means “sheath.” Beetles have hardened front wings called elytra that cover, or sheath, their hind wings and abdomens. When beetles fly, they swing their elytra forward to fly around on the hind wings. It’s why many aren’t good fliers, earning them the alternate common name “bumbling beetles.” Join the prefix, coleo, to the suffix, ptera, and voilà! You have the bumbling beetle order Coleoptera, which clearly describes its members.
Insects like the milkweed bugs and the false milkweed bug have front wings that are half-hardened and half-membranous. The prefix “hemi” is derived from the ancient Greek for “half.” Adding the suffix- ptera produces the name Hemiptera, which means “half wing.”
Somewhere along the line, entomologists threw the public a bone by deciding they would use the common name “True Bugs” for members of the order Hemiptera. After all, most people generally call insects and spiders “bugs.”
Originally, insects like cicadas, aphids, planthoppers, etc., were grouped in their own order, Homoptera. The name of the order was based on homogeneous front wings. The front wings are either all membranous like cicadas or all leathery like hoppers. They aren’t divided into septate parts like hemipterans.
However, taxonomists never sleep. They decided to eliminate the order Homoptera and move its members into several suborders under the order Hemiptera.
The original members of Hemiptera retained their “true bugs” common name, but the sleep-deprived taxonomists placed the true bugs in a new suborder, “Heteroptera.” The name is derived from the Greek word hetero, meaning different, which was a nod towards the differing structures of their front wings, with areas that are hardened attached to areas that are membranous.
Since false milkweed bugs belong to the suborder Heteroptera, they are, in fact, true bugs. As I said, taxonomy can be taxing.
Selected References
Carlson, N. J., Hastings, A. P., Duplais, C., & Agrawal, A. A. (2026). Divergent dietary and defensive adaptations of closely related coexisting seed bugs. Proceedings of the National Academy of Sciences, 123(8), e2535697123.
https://www.pnas.org/doi/abs/10.1073/pnas.2535697123
Slater, J. A. (1983). On the biology and food plants of Lygaeus turcicus (Fabr.)(Hemiptera: Lygaeidae). Journal of the New York Entomological Society, 48-56.
https://www.jstor.org/stable/25009340
