Swallowtail vs Monarch: How to Tell Them Apart

At a glance, some swallowtails and monarchs can look similar enough to cause genuine confusion, especially when they are nectaring at the same flower and you only catch a glimpse of one in flight. But once you know the key differences, you will rarely mix them up again. The two groups belong to entirely different families and have very different wing shapes, flight patterns, and life history strategies.

This comparison focuses on the most useful field marks and behavioral cues, things you can actually use when a butterfly lands in your garden for a few seconds. You do not need a field guide or a net to tell them apart once you know what to look for.

The Most Obvious Difference: Wing Tails

The defining feature of swallowtail butterflies is their hindwing tails. These are elongated projections that extend from the lower edge of the hindwing, giving the butterfly a distinctive swept appearance. The name “swallowtail” comes directly from the resemblance to the forked tail of a barn swallow in flight. Not every swallowtail species has equally prominent tails, but all North American swallowtails have at least some extension on the hindwing.

Monarchs have no tails at all. Their hindwings are rounded and smooth along the lower margin. If a butterfly you are watching has any kind of pointed projection at the lower back of the wing, it is not a monarch. That single observation eliminates the monarch from consideration immediately.

The tails on swallowtails vary considerably by species. Eastern tiger swallowtails have long, prominent tails. Pipevine swallowtails have shorter, stubbier tails. Spicebush swallowtails have medium-length tails with a spatula-like shape. But all of them have something at the hindwing tip that monarchs simply do not have.

Size Comparison

Monarchs are mid-sized butterflies with a wingspan of about 3.5 to 4 inches. That sounds large, but many swallowtails are bigger. The eastern tiger swallowtail regularly reaches 4 to 5.5 inches in wingspan, making it noticeably larger in the field. The giant swallowtail can reach up to 6 inches, which makes it the largest butterfly in North America.

Some swallowtail species, like the pipevine swallowtail and the spicebush swallowtail, are closer to monarch-sized, with wingspans of 3 to 4 inches. With these species, size alone is not a reliable separator. You need to look at shape and color as well.

When two butterflies are nectaring together, size comparison is easy. But when you are looking at a single butterfly in isolation, estimating size is harder. That is why multiple field marks are always more useful than any single feature.

Color and Pattern Differences

The monarch has one of the most consistent color patterns of any North American butterfly. Both males and females are deep orange with black veining and a black border dotted with white spots. The underside is slightly paler orange with the same pattern. There is almost no variation between individuals, and you will not encounter a yellow or blue monarch in nature.

Swallowtails come in a much wider range of colors and patterns across species. Eastern tiger swallowtails are yellow with black stripes and a band of blue along the hindwing. Black swallowtails are mostly black with yellow and blue spots. Zebra swallowtails are pale green with black stripes and red and blue accents. Pipevine swallowtails are black with iridescent blue-green on the hindwing. The variety within the swallowtail group is far greater than within the monarch group, which contains essentially one main color form in North America.

Female eastern tiger swallowtails add another layer to this. They have a dark form, which is almost entirely black with a hint of the tiger stripe pattern and a band of blue on the hindwing. A dark female tiger swallowtail can look superficially similar to a pipevine or spicebush swallowtail, but it looks nothing like a monarch. Our swallowtail species identification guide covers these color variations in more detail.

Wing Shape and Flight Style

Beyond the tails, the overall wing shape differs between the two groups. Monarchs have broad, rounded wings with a somewhat rectangular outline. The forewings are slightly more elongated than the hindwings, but the overall silhouette in flight looks fairly uniform. Monarchs glide frequently, holding their wings in a shallow V-shape (called a dihedral) and covering long distances with minimal wingbeats between glides.

Swallowtails typically have wings with more complex outlines. The tails obviously change the shape, but even beyond the tails, many swallowtail species have scalloped or wavy hindwing margins. In flight, swallowtails tend to flap more actively than monarchs and glide less. The tails also move and flutter as they fly, which gives swallowtails a distinctive flickering appearance in the air.

Monarch flight has a characteristic “flap, flap, glide” rhythm that experienced observers can recognize at a distance before they can even make out wing color. Swallowtails do not have this same predictable rhythm. Once you have watched a few dozen monarchs in flight, you will start to recognize that pattern from across a field.

Family and Classification

Monarchs belong to the family Nymphalidae, the brush-footed butterflies. Swallowtails belong to the family Papilionidae, which is a completely separate family. These two groups diverged from a common ancestor hundreds of millions of years ago, and their differences in wing structure, host plant use, and anatomy reflect that deep evolutionary separation.

Papilionidae, the swallowtail family, contains about 600 species worldwide and is considered the most basal butterfly family, meaning it branched off earliest in butterfly evolution. Members of this family tend to be large, have fully functional front legs (unlike Nymphalidae, where the front legs are reduced), and many have the characteristic hindwing tails.

One behavioral difference tied to family membership is the caterpillar defense. Swallowtail caterpillars have a forked, orange gland called an osmeterium behind their head. When threatened, the caterpillar extends this gland and releases a foul-smelling chemical. Monarch caterpillars have no such gland. They rely on the toxins they absorb from milkweed instead.

Host Plants

Monarchs are exclusively milkweed feeders as caterpillars. They will not survive on any other plant. This specialization is part of why monarch populations are tied so closely to milkweed availability across North America.

Swallowtail caterpillars feed on a wider variety of host plants, though each species has its own preferences. Eastern tiger swallowtails use trees like wild cherry, tulip poplar, and birch. Black swallowtails prefer plants in the carrot family, including dill, fennel, and parsley. Giant swallowtails specialize on citrus and related plants. Pipevine swallowtails feed exclusively on Aristolochia plants. The diversity of host plants among swallowtails reflects the diversity of the group itself.

Mimicry and Look-Alikes

The monarch has a well-known mimic in North America: the viceroy butterfly. The viceroy evolved to resemble the monarch closely, gaining protection from predators that have learned to avoid the toxic monarch. The viceroy is smaller than the monarch and has a black horizontal line crossing its hindwing that monarchs do not have. No swallowtail species closely mimics the monarch.

Within swallowtails, the pipevine swallowtail serves as the model for a mimicry complex. Spicebush swallowtails, female black swallowtails, dark-form female tiger swallowtails, and red-spotted purples all mimic the pipevine swallowtail’s coloration. The pipevine swallowtail, like the monarch, is toxic due to chemicals sequestered from its larval host plant. This is a different set of relationships from the monarch mimicry complex, and none of the pipevine mimics look anything like a monarch.

The monarch’s orange coloration is its own warning system, and no swallowtail has evolved to copy it precisely. If you see a large orange butterfly with black veining and white spots in a black border, you are almost certainly looking at a monarch or its mimic the viceroy, not a swallowtail. Our guide to monarch wing colors goes into more detail on what each part of that pattern communicates.

A Quick Field ID Summary

When you spot a butterfly and want to know quickly whether you are looking at a swallowtail or a monarch, run through these checks in order. First, look for hindwing tails. If they are present, it is a swallowtail. If the hindwings are smooth and round with no projections, it could be a monarch. Second, check the color. Orange with black veins and a spotted border points to monarch. Any other color scheme points to a swallowtail or something else entirely. Third, watch the flight. Monarchs glide more than swallowtails, and their wingbeats have a slower, more measured rhythm.

That three-step check handles almost every identification challenge you will encounter in a North American garden. If you are still unsure after running through it, the butterfly you are looking at is probably a swallowtail species or a viceroy, not a monarch.

Key Takeaways

• Swallowtails have pointed hindwing tails that monarchs completely lack, making wing shape the fastest and most reliable way to tell the two groups apart.
• Most swallowtail species are larger than monarchs, though some overlap in size exists with medium-sized swallowtails like the pipevine and spicebush.
• Monarchs have a consistent orange, black, and white pattern, while swallowtails come in a wide range of colors spanning yellow, black, green, and iridescent blue.
• Monarchs and swallowtails belong to entirely different butterfly families (Nymphalidae and Papilionidae) and have different host plants, caterpillar defenses, and flight behaviors.

Frequently Asked Questions

Can a swallowtail butterfly look like a monarch?

No swallowtail species closely resembles a monarch. Swallowtails have hindwing tails and very different color patterns. The butterfly most often confused with the monarch is the viceroy, which is a member of Nymphalidae like the monarch, not a swallowtail at all.

Which is bigger, a swallowtail or a monarch?

Many swallowtail species are larger than monarchs. The eastern tiger swallowtail and the giant swallowtail both exceed the monarch’s wingspan of 3.5 to 4 inches. However, some swallowtails like the pipevine swallowtail are similar in size to the monarch, so size alone is not a reliable identification tool.

What butterfly is most often mistaken for a monarch?

The viceroy is the most common look-alike. It is orange with black veining like the monarch, but it is slightly smaller and has a black line running across its hindwing that monarchs do not have. Swallowtails are rarely mistaken for monarchs because their wing shape and coloring are so different.

Do swallowtails and monarchs visit the same flowers?

Yes, frequently. Both groups are attracted to nectar-rich flowers like milkweed blooms, coneflowers, zinnias, and butterfly bush. Seeing both at the same plant at the same time is common in butterfly gardens, which is part of why people want to be able to tell them apart quickly.

Are swallowtails related to monarchs?

Swallowtails (family Papilionidae) and monarchs (family Nymphalidae) are both butterflies in the order Lepidoptera, so they share a distant common ancestor. But they diverged from each other hundreds of millions of years ago and are not considered close relatives within that order. They are about as distantly related as two butterfly families can be.