Sunday, June 23, 2024

The winter form of the eastern comma butterfly is orange with black spots. (Photo: Jeffrey Offermann)

The eastern comma (Polygonia comma) butterfly is one of the earliest spring butterflies we see. Polygonia is Greek for “many angles,” and this butterfly has wings with many angles rather than the smooth wings of other butterfly species. Eastern commas do not rely on flowers for nectar like other butterflies. Instead, they feed on sap, animal droppings, rotting fruit – they especially like overripe bananas – and the salts and minerals in puddles. It is not always easy to spot one of these butterflies, because when its wings are folded, it looks like a dead leaf. In the center of the folded hindwing is a white mark, similar to the letter C or a comma (hence its name).

Eastern comma caterpillars sometimes are found on hops. For this reason, farmers once called this butterfly “the hop merchant.” Farmers said they could predict the future price of hops by the silver and gold spots on the chrysalis: If the spots were gold, hop prices would be higher; if the spots were silver, hop prices would be lower.

When its wings are folded, you can see a white “comma” or letter C on the hindwing. (Photo: Tom Murray)

When its wings are open, the top of the wings are orange this time of year. These are winter butterflies that have endured the cold temperatures and become active again. The female lays eggs early in the season. By midsummer, these eggs will have produced summer butterflies. The open wings of the summer butterfly have more black on the wings than the winter butterflies. This butterfly has a wingspan of up to 2 inches, so it is fairly small.

In Massachusetts, look for the orange winter form to fly from late September through November, to hide and hibernate during the winter, andto fly again from March through May. Look for the dark summer form to fly from late June to late August. Although the winter butterflies hibernate, you might be able to spot one flying on a warm winter day, out briefly before returning to its hibernating spot. These butterflies overwinter in rock crevices, tree cavities, under bark or in other protected areas. Because their blood contains glycerol, which acts as an antifreeze, their tissues avoid cell damage during winter freezes.

An eastern comma butterfly drinks sap from a tree felled by a beaver in Groton. (Photo: Tom Murray)

They emerge from their winter shelter during the first sunny spring days to lay eggs, which become caterpillars. Each caterpillar grows slowly before it forms a chrysalis. Just as winter butterflies hibernate during the cold, summer butterflies become dormant when temperatures are very hot. By September, the dark summer butterflies are gone and new orange winter butterflies begin to emerge. The winter butterflies can sometimes be spotted as late as November, but then they find a protected place to overwinter.

This butterfly lays green, ridged barrel-shaped eggs on plants that can host the caterpillars. Host plants include nettles, gooseberries, elm saplings and hops. After about two weeks, the eggs hatch into caterpillars that vary in color from pale green to yellow to white to black. The caterpillars feed at night and hide on the underside of leaves during the day. As the caterpillars get older, they pull a single leaf together with silk to build a daytime leaf shelter, but still emerge only at night. After about four weeks, the caterpillars are fully grown, slightly more than an inch in length. Each caterpillar metamorphoses into a chrysalis that is brown and covered with spines. The chrysalis stage lasts for a week or two until a butterfly emerges.

The summer form displays dark hind wings. (Photo: Tom Murray)

Look for this butterfly near water. Males perch in the sun waiting for females to approach. The males are territorial and will chase other butterflies and insects away from its sunny territory. Sometimes they even chase birds! According to Samuel H. Scudder (1889) in The Butterflies of the Eastern United States and Canada: with Special Reference to New England:

They are very wary insects with a quick, nervous flight, yet at the same time audacious even to pugnacity, darting recklessly at and about objects in the air, vainly pursuing even passing birds or dragonflies, and tussling with each other to such an extent that their wings are almost invariably rubbed and ragged in a short time.

The eastern comma butterfly relies on two habitats: open areas with caterpillar host plants (hops, nettles, elm saplings) and forests for hibernation. These butterflies may hibernate miles from food plants.


Seen nearby

Jeffry Powell spotted these frisky killdeer in the Parker River National Wildlife Refuge in Newburyport on April 18.


Have you taken photos of our urban wild things? Send your images to Cambridge Day, and we may use them as part of a future feature. Include the photographer’s name and the general location where the photo was taken.

Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.

This post was updated April 26, 2023, to correct the spelling of Jeffrey Offermann’s name.