Wild Side : American ladies are beautiful and plentiful on Martha's Vineyard
Photo by Matt Pelikan
With the beginning of June and the end (one hopes) of this year's dismal spring weather, the butterfly season is in full swing on the Vineyard. Perhaps two dozen species are currently active. Many of these, regrettably, are small or drab, or both, and hence unlikely to be noticed by casual observers. But one species that nearly anyone should be able to find is the American lady.
About two inches across, the American lady is fairly large for a butterfly, though it's distinctly smaller than the show-stopping monarchs and swallowtails that represent some people's image of a butterfly, American Ladies are conspicuous by virtue of their color — orange above with webbing of black. The underside is less garish, with complex mottling, but displays this insect's most useful field mark: two large, black "eyes" on the hind wing. (A close relative, the painted lady, is usually much less common here and can be recognized by four much smaller eye spots on the hind wing.)
American ladies are active butterflies, and widespread both on the Vineyard and on the continent at large. They fare surprisingly well in human-dominated habitats: though you may not have noticed them, one has certainly visited your yard.
Like most butterflies, American ladies will drink nectar from nearly any kind of flower, but this species has a particular weakness for Buddleia, or butterfly-bush, blossoms. It's not uncommon to find a half-dozen American ladies on one of these bushes. Female American ladies are particularly restless, flying incessantly low over the ground, exploring for a suitable plant on which to lay their eggs.
As is the case with most butterflies, American lady caterpillars are rather fussy about what they'll eat. If they have to, these caterpillars can survive on a wide range of plants, mainly members of the aster family. Across the continent-wide range of this species, its larvae have been found using dozens of plant species. But in our region, American ladies show a very strong preference for pearly everlasting and pussy-toes, two aster relatives with grayish, fuzzy leaves, which grow here both wild and as ornamentals. If you have either one in your garden, you can be certain that a female American lady will sniff it out, half-perch and half-hover over a leaf, wrap the tip of her abdomen to the leaf's underside, and delicately paste a tiny greenish egg on the leaf.
The eggs hatch in a few days to reveal tiny orange or yellow caterpillars, just a few millimeters long. Over the next few weeks, these larvae will graze on the plants, growing steadily larger. Part of the appeal these plants have to the caterpillars probably has to do with the fuzziness and flexibility of the leaves.
Producing fine threads of silk, the caterpillars tie leaves up into cozy shelters, which protect the caterpillar from predators and help it regulate its temperature. These shelters are easily seen when present: untidy bundles containing the caterpillar and usually a bunch of caterpillar droppings. When the caterpillar is mature, it enters a dormant state called a pupa, reconfiguring its tissues to emerge as an adult butterfly.
Interestingly, authorities differ on what American ladies do during the winter. It was long assumed that this butterfly overwinters, either as a pupa or as an adult, throughout most of its range. Currently, though, the thinking is that American ladies don't tolerate prolonged hard freezes and either don't overwinter, or do so in small numbers, at our latitude.
Much of the population migrates south in the fall, spending the winter in the species' "core range" in the southern states. With the warming of spring, the species expands northward again, recolonizing the northern parts of its range. Certainly most early-season American ladies appear to be on the move, rarely lingering in one spot and generally heading north. And in September and October, southbound migrants are usually quite evident on the Vineyard, lending credence to the migratory theory.
In any case, American ladies exhibit a long season on the Vineyard, with the first individuals typically turning up in mid-April and the last ones persisting into November. The species has been found here as early as April 4 and as late as December 5, giving it one of the longest seasons of any Vineyard butterfly. While it is reliably present on the Island every year, the American lady varies widely in numbers. But most seasons (and 2011 is looking quite typical), this species is common enough so I encounter it every time I'm in the field and find it daily in my yard.
A beautiful and adaptable insect, the American lady can occur literally anywhere on the Vineyard. Grow its caterpillar food plant, and you'll likely be able to witness its life cycle up close. And even if it just visits, this butterfly brings a welcome bit of the wild into our yards and gardens.