Thistles provide a good nectar source for migrating Monarchs. These tall flowers also provide good opportunities for photographing butterflies against a clear blue sky.
Monarch numbers usually peak in late August and September, when migrants start heading back south. (These migrants are descendants of the first generation that arrived earlier in the year - not the same butterflies that made the journey from Mexico.)
These famous migrant butterflies overwinter in Mexico and repopulate much of North America every year. The first arrivals typically reach Ohio in May or June. I have one early sighting on April 17, 2017.
This is a male Monarch nectaring on stiff goldenrod. Male Monarchs can be told apart from the females by the dark scent glands on their hindwings.
This Monarch is sipping sunflower nectar at Sugarcreek MetroPark.
This Monarch was photographed at Cox Arboretum on November 5, 2017. Late season stragglers can linger into November, although ideally they would be better off in Mexico by this date. Even if the weather stays mild, Monarchs start running out of nectar sources if they linger into November.
Close-up of Monarch on wingstem flowers at Huffman Prairie.