Friday, May 11, 2007
Spring azure butterfly
When and where seen. I saw dozens of spring azures on Heartbreak Ridge in Great Brook Farm State Park on May 4 and at the Cranberry Bog on May 5. They are also in my backyard. The earliest I saw one this year was April 28 and not in Carlisle but at Weirs Hill in North Andover.
Identification. First, the easy part: the spring azure has an almost uniform violet-blue color on the topside of the wings. This is the color you notice as they flit about. The forewings of the female have a black border. The underside of the wings is gray with variable black markings. When the butterfly is at rest, the wings are held together above the back displaying the underside markings as in the photo. The black and gray colors with no trace of blue provide a good amount of camouflage. The butterflies are small with a wing span of three quarters to one and a quarter inches. Now for the tricky part of identification: patterns on the underside of the wing can be identical in C. ladon and C. lucia so it's possible the one in the photo is C. lucia not C. ladon. To distinguish the species, you need to look at the structure of the scales on the topside of the male's wing "with a trained eye." I didn't know this until I had released the one I caught — which coincidentally was a male. Even if I had known, it would have been difficult to get a good look at the wing scales without sacrificing the critter. Other factors that play a role in positive identification are habitat, flight dates, and whether this is an early, late or normal spring — further complicated by the fact that "normal spring" in New England is probably an oxymoron. It's normal because it's either late or early. Sometimes it's both with an early tease followed by a late lingering wintery punishment.
Caterpillars. The base color of caterpillars within the species complex is usually a nice spring green but can also be brown, pink or white and they can have a variety of patterns. They get to be just over half an inch long and have lots of white star-shaped hairs. The hairs are very short except along the lower edges of the sides and at the rear.
Habitat. Spring azures like open parts of deciduous woods, brushy areas, streamsides, and clearings in and around wooded areas. Host plants include dogwood, viburnum and blueberry.
References. Robert Michael Pyle, Audubon Field Guide to North American Butterflies, David L. Wagner, Caterpillars of Eastern North America; Bug Guide at http://bugguide.net/node/view/223.
Submissions for the Biodiversity Corner are encouraged from everyone. What are you finding? Send a note to Kay Fairweather at 392 School Street, Carlisle MA 01741 or to email@example.com.
© 2007 The Carlisle Mosquito