Butterfly identification can be extremely challenging. Often times only a slight variation in colour or marking is what separates two similar butterflies. Their small size combined with their propensity to not stay motionless very long often adds to the challenge of identification. Knowing what to look for can help achieve a quick and positive identification.
Two virtually identical butterflies found in Southwestern Ontario are the Monarch and the Viceroy. At a quick glance these two butterflies can easily be mistaken for each other. Fortunately, there are a few distinguishing characteristics I look for when out in the field to differentiate between the two.
The most obvious way to tell the difference between a Monarch and a Viceroy is by looking at their hindwings. The Viceroy displays a black line that runs across the hindwings, which the Monarch does not have. This line is visible from both the top and bottom making it particularly easy to see when the butterfly is at rest.
A second but less obvious way to separate the Monarch from a Viceroy is by size. Monarchs typically have a larger wingspan than a Viceroy; however, a large Viceroy and small Monarch can have almost the same wingspan, so this characteristic is less dependable.
The third way I differentiate between a Monarch and a Viceroy is by their flight pattern. A Viceroy’s flight is much more erratic and less graceful than that of a Monarch. A Monarch tends to fly smoothly often gliding while making slow turns, whereas a Viceroy displays a more rapid wing beat, glides less frequently, and makes faster, sharper turns.
Perhaps the real challenge of butterfly identification is getting a long enough look to observe any or all of these unique characteristics that each butterfly displays. If you see one of these butterflies and are unsure whether it is a Monarch or Viceroy remember these three traits.
When I am out in the field and see a butterfly in question I quickly run through these 3 characteristics in my mind. If the butterfly is in flight, I will observe the size and flight pattern to get an accurate identification. With lots of practice I can now confidently recognize the flight pattern of either butterfly. I will then watch for the butterfly to land and when it does, I quickly look to see whether or not the butterfly displays a black line across the hindwings to make certain of my identification.
Next time you are out in the field and question whether you see a Monarch or a Viceroy, try observing these characteristics to assist you with identification. As mentioned previously, looking for the black line across the hindwings is by far the easiest and most accurate method to positively identify these similar butterflies, but with a little time and practice recognizing size and flight pattern will soon become apparent too.
Southwestern Ontario is home to a wide variety of butterflies and getting out during the summer months to enjoy their beauty is especially satisfying. I think you will find that recognizing these three characteristics will be incredibly useful in helping you positively identify Monarch and Viceroy butterflies.