Wild Side : Butterflies on Martha's Vineyard are varied and very interesting
Photo by Matt Pelikan
People whom I introduce to butterfly watching are often disappointed to find that the majority of the Vineyard's butterfly species are small, or drably colored, or both. We certainly have our show-stoppers, like the stunning, black-and-yellow tiger swallowtail. But the evolution of most of our butterflies seems to have been shaped mainly by the desire not to get eaten, and not being spotted in the first place is a useful step toward achieving that. Small and drab are safe things for insects to be.
But there is a positive side to tiny, dull butterflies. Because they conceal themselves effectively and don't take up much space, they can flourish in surprisingly small patches of habitat. And relatively large numbers of them can occur in a small area. From the observer's perspective, this means that broad distribution compensates for the unobtrusive nature of these insects: if you have a yard, several of these less dramatic butterflies are surely breeding there, or at least visiting regularly from breeding sites nearby. With a little attention, you can spot them.
A family of species known familiarly as the "grass skippers" typifies these common-but-cryptic butterflies. All in all, 17 members of this group are known from the Vineyard. A couple of these species are rare, and one disappeared from the Vineyard sometime during the mid-20th century. But still, common (or at least regularly occurring) grass skippers account for almost one-quarter of the Island's total butterfly diversity.
The caterpillars of grass skippers live, as the name of this family suggests, on grasses, native ones in most cases. And adults, fittingly, occur most often in open, grassy areas, with their preferences ranging from dry grassland to freshwater marsh, depending on species. Each type of skipper has a fairly specific grass preference for its caterpillar food plant, and adults will most often be found in habitat that supports the grass or grasses that the larvae of its species depend on. Not too surprisingly, human residential areas offer suitable habitat for many species on this list, as long as a diversity of native grasses persists among the lawns and exotic plantings, and as long as the effects of pesticides are limited.
Adult grass skippers range in size from about a half-inch long, in the case of the aptly named least skipper, to about an inch in the case of the broad-winged skipper. Generally speaking, these butterflies are small-winged and large-bodied; despite the unpromising aerodynamics that result, most skippers fly like bullets, their velocity making them very difficult to track in the air.
Happily, due in part to the energetic demands of their flight, adult skippers are notorious chow-hounds: a good portion of their time is spent refueling on nectar from flowers, and it is while they are doing this, their wings and bodies often silhouetted on top of a flower, that there are most easily observed. Moreover, adults (especially males) often bask on exposed perches, giving off special scent chemicals that attract the opposite sex.
You need to calibrate your eyes for spotting insects this tiny, but once you develop the knack, you'll start to realize just how many skippers are around. Grass skippers all share a distinctive posture when at rest: the hind wings often project horizontally from the body, with the forewings raised at a 45-degree angle. Skippers don't always pose like this, but few other butterflies are likely to be seen in this posture.
Several of our most common skippers exhibit a peak of activity in early June. Of the species active now, most go through multiple generations in the course of year, meaning that they will show additional periods of abundance later in the season.
The tiny least skipper, orange-winged with an uncharacteristically slender body for a skipper, is one June species that commonly occurs in yards. It actually prefers wetland edges, but damp, partially shaded corners of yards apparently work for it as well. The tawny-edged skipper, a muted golden-brown underneath with no distinctive markings, is even more widespread, with a preference for dry areas. And Peck's skipper, with prominent yellow patches on the undersides of its wings, may be even more numerous.
Overall, the season for skippers on the Vineyard is a long one. First to appear, as early as the first week of May, is the cobweb skipper, a drab but intricately marked butterfly that is unfortunately fussy about its habitat — it's a bluestem grassland specialist and rarely turns up far from this setting. The last skipper to take wing is Leonard's skipper, brick red with a bold band of white spots under its hind-wing, which flies starting in late August. But the last generations of some other species mature even later, meaning that overall, our skipper season extends into mid-October.
Skipper identification challenges even experienced observers, and it will take a field guide, not just a Wild Side column, to help you successfully put names to these tiny butterflies. But the first step of identification is to recognize the general group to which an organism belongs. So knowing a skipper when you see one will help get you into the right part of your field guide. And knowing the habitats of these excellent butterflies will help you notice them in the first place.