Hey ladies. Though it sounds like it could be a catcall on a city street, this greeting is of a more rural (or even floral) variety. It is actually a beckoning to butterflies.

Two types of ladies have been making the rounds, flitting and fluttering from flower to flower. American and painted ladies, Vanessa virginiensis and Vanessa cordui respectively, can be found flying in the fall.

The American lady is the more commonly seen species in our neck of the woods. However, it is the painted ladies that have my eye this season, as I have been noticing gregarious groups of gathering butterflies.

It seems that an irruption is afoot (or, more accurately, a-wing)! Reports of large numbers of painted ladies have been numerous and wide reaching. A 70-mile wave of these wonders was reported last month near Denver, Colo.

In Massachusetts, ladies are considered irruptive migrants. This describes movement that is independent of any season or geographic patterns. These butterflies are not ladies of leisure; they are able to reach speeds of 30 miles per hour and cover distances of up to 100 miles in their migration.

In this case, these butterflies came north, and bred successfully and plentifully. However, since the painted ladies cannot overwinter here, they must either return south or perish when the colder weather comes.

American ladies are a bit more cold tolerant than painted ladies, and might be able to overwinter here as adults or larvae. This is not the only difference between the species, which are generally similar in appearance and behaviors. Both share the orange and black coloring on the upper side of the wings, and have brown cobweb patterns with obvious ‘eyespots’ on the wing’s lower side.

There are subtle differences, though, and now is a good time to learn them, while both varieties are winging about. Start with wing shape. The American lady’s wings are somewhat squared off at the top, while the painted lady’s are more pointed. Then consider the view from above. A small white dot is found on the American lady’s upper mid-forewing, which is absent in the painted lady. If the insect stays still long enough, look on the underwing. Count the large eyespots on the lower underside wings for a definitive identification. The American lady has two large eyespots on their underwing, while the painted lady has four smaller, but still significant ones.

Then, there is food. Painted ladies, also called thistle butterflies, forage for nectar on these favorites: thistles, cosmos, privet, blazing star, ironweed, Joe pye weed, clover and buttonbush. American ladies like dogbane, vetch, goldenrod, and marigolds. Both enjoy sweet syrup from asters and milkweeds.

The painted ladies also seem to be grouping together, with multiple individuals sharing shrubs and flowers (hopefully energizing up for a southward flight). Let’s hope the weather won’t be a lady-killer and that they find their way to warmer whereabouts.

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature.