BUG OF THE MONTH SUPPLEMENT
A New Washington Butterfly
Order Lepidoptera, Family Hesperiidae
Copyright © 2002 by Robert Michael Pyle
This article originally appeared in Scarabogram, August 2002, New Series No. 268, pp. 3-4.
We have a new member of the Washington butterfly fauna. On Friday, July 12 , Thea Pyle and I investigated several sites along the BC-WA international border in search of the European Skipperling, Thymelicus lineola. We have long expected this introduced species to reach Washington, and have searched along several sections of the northern and eastern borders. Just back from New England, where we were inundated with the handsome small Essex Skippers (as they are known in the UK), we were encouraged to have another look.
|Thymelicus female nectaring, West Virginia
© Randy Emmitt, used with permission
|Thymelicus male mudding, West Virginia
© Randy Emmitt, used with permission
There have been at least two prior introductions in British Columbia. Scarab Merrill Peterson had earlier reported seeing them not too far north into BC along the freeway, so we first visited Birch Bay and Blaine, and in particular the Peace Arch International Park, where one has free access back and forth across the landscaped border zone on foot. In spite of abundant nectar, especially in the better-financed BC portion of the park (marigold, alyssum, and other popular skipper nectar sources), no butterflies were apparent on the warm, clear morning except for one female Pieris rapae visiting fish fertilizer. The lawns, of course, are close-cropped here.
Next we drove east through Blaine, parallel to the border. Just east of town, D Street crosses a major N/S powerline at T41N R1E S32. Since powerline rights-of-way, if not sprayed, often furnish excellent butterfly corridors, we took a look. I no sooner left the car than I saw the first skipper. Thea netted it, thus becoming the captor of the state record vouchers for this species in three states: Idaho and Montana in 1991 and Washington in 2002. We proceeded to collect a series of twelve individuals from this site from among the many hundreds on the wing. Every individual examined was a fresh male, so apparently we arrived right at the beginning of mass emergence. Some individuals were still drying wings; others were nectaring on white clover, hawkbit, bramble, and other weedy flowers, or fluttering slowly. While they do have a higher gear, these skippers fly noticeably more deliberately than most hesperiine (=monocot-feeding) skippers. The power-line jogs east along the border, and crosses a big, weedy gravel pit that fronts on D Street. This area too was well populated with European Skipperlings. The only other butterflies seen were a few Western Tiger Swallowtails, Lorquin's Admirals, and Cabbage Whites.
Over the next few hours, we investigated various sites eastward. T. lineola appeared along roadsides, in timothy/rye hayfields, red/white clover hayfields, and weedy edges nectaring on purple vetch, Vicia cracca, a favorite nectar plant in the East. Finally, late in the day, Thea netted one individual on a weedy pink pea below the new bridge of SR 542 over the Nooksack River, due northeast of Bellingham at T39N R4E S28. So the butterfly has colonized an area at least from Blaine east to Sumas and south to Cedarville -- a good chunk of northwestern Whatcom County. Nowhere was it as abundant as at the original powerline site, so the edge of the advance is probably still sparse. I suspect we found the species within a very few years of its border crossing. Recalling that Ray Stanford was way too conservative in his estimate of the species' arrival in Colorado, I predict that T. lineola will reach the Puget Sound basin (Salish Lowlands) within three to five years. Since it overwinters as eggs, a rare condition among skippers, it can easily be transported in hay, so that spontaneous irruptions can occur independent of the advancing front of colonization.
I consider the European Skipperling an essentially positive addition to the Western Washington butterfly fauna, which, as most know, is fairly impoverished. I doubt that it will have any deleterious effects on the native fauna or flora, as it utilizes weedy resources for the most part. It is attractive, interesting, and capable of abundance we seldom see. This will give us an earlier summer skipper as common as the later summer Woodland Skipper, not an unwelcome addition for butterfly watchers, and an interesting object of study for lepidopterists interested in ecogeography. Incidentally, the only other species observed in several of the skipper stations was Pieris rapae, the European Cabbage White: a wry observation in a countryside dominated by Dutch dairy, berry, and hay farmers.
The Washington butterfly fauna now stands at 147, more or less. Maybe we'll hit 150 after all, or drop back, if some of the recent splits don't hold. A nice dorsal photograph of Thymelicus lineola, photographed by John Lane in Charles Remington's back yard in Totoket, Connecticut, appears in The Butterflies of Cascadia. The species account tells what we know of its ecology and expansion since introduction around 1910 in Ontario.
One final note: I was prepared for, and expected, a degree of observation of ourselves as we scoured the borderlands -- just as I experienced in 1996 as I followed the Monarch migration along the Mexican border (several such Border Patrol encounters reported in Chasing Monarchs). So I was amused, but not surprised, when (as I was examining the shore of a little lake on private land abutting the border northeast of Lynden) a fairly large helicopter approached from the west, paused directly overhead, and slowly circled us for ten minutes. I peered back, waved, and went on sweeping the vegetation with my net, at which point the helicopter veered away. And yes, it was black.
Pyle, Robert M. 1999. Chasing monarchs : migrating with the butterflies of passage. Houghton Mifflin, Boston, 307 pp.
_____. 2002. The butterflies of Cascadia : a field guide to all the species of Washington, Oregon, and surrounding territories. Seattle Audubon Society, 420 pp.
Web pages on this species:
at Butterflies of North America
an Italian page with good larva-pupa photos
a British page with good European info