How do you tell a monarch apart from a viceroy or other mimics?

It is easy to mistake a viceroy or other mimic for a monarch. Viceroy butterflies are commonly mistaken for monarchs. They are slightly smaller in size than monarchs, but their largest distinguishing feature is a thick black horizontal (when wings are open) stripe across both hind wings that is missing from monarchs. If you see that distinct stripe, it's a viceroy! The caterpillars and eggs look very different from immature monarchs. For more information about the differences between viceroys, monarchs, and other mimics, download the Monarch SOS app for Apple devices, or see this detailed description from Journey North.

Swallowtail caterpillars are predominately green with yellow dots compared to the yellow, white, and black stripes found on monarch caterpillars. Swallowtails are commonly found on parsley and dill whereas monarchs will only be found on milkweed.

Queen butterfly caterpillars look very similar to monarch caterpillars however the biggest identifier is the 3rd pair of tentacles found on the thorax of the queen caterpillar. Adult queens can be distinguished from adult monarchs by the presence of white dots found on the orange pattern of the forewings. On monarchs, the white dots are contained to the black edges of the wings and do not come in contact with the orange wing cells.