July is the butterfly month in the Northland. No other month can match this hot month of summer in numbers and variety of these insects. On nearly any clear day, a searcher can find 20 or more kinds. Most are colorful and easy to see as they come to flowers of our yards, gardens and fields. Here they find a plant in bloom and settle down for a meal of nectar. They range in size from skippers of less than one inch long to the black-yellow tiger swallowtails that may have a wingspan of more than 4 inches. These delightful "flying flowers" add a great deal of beauty and interest to these warm-season days.
And the butterfly diversity does not end with the open areas. Within the more shaded woods are a few more butterflies not as colorful. Butterflies that are brown to black, living in shade, and feeding on sap, rotten fruit and dung are certainly different from the norm. But three kinds flourish here.
Little wood satyrs, only about 1 1/2 inches across when in a spread wing pose, are the first to appear. They have been with us since late June. Along the edges of their light brown wings is a series of dark dots. Forewings hold two black spots while the hindwings have two above, four below. When the butterflies close their wings, only the four spots of the under hindwing are visible.
Biggest and darkest of these drab midsummer butterflies is the common wood nymph. During late July at the edge of the woods, these dark butterflies take wing. Looking nearly black with a large circular spot on the forewing, these 2 1/2-inch insects move from the woods to the open regularly. Some sport a light color rectangle on the front wing near its dark spot. Others are completely dark.
Maybe the most common of the less colorful summer butterflies is the northern pearly-eye. In the woods, often near streams or marshes, this 2-inch critter flutters by. The northern pearly-eye gets its name from the 20 "eyespots" that mark the otherwise brown wings. (Eyespots are dark colorations that may be entirely dark or with a lighter center, thus looking like an eye.) A light color pearl-like marking appears in the center of each eyespot on the underside of the hindwings.
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Living in the forest, they forego nectar, feeding instead on sap from various trees. These include willow, poplar, and birch. They have also been known to come to clothes left outside. Apparently, these brown butterflies have a taste for moisture and sweat in the fabric.
Adults live for two months during summer. With this cryptic brown camouflage, they are able to bask on bark with safety despite their 2-inch wing span. The numerous eyespots, seen on the underside, intimidate other critters by making the pearly-eye appear to be full of eyes. To possible predators, the butterfly may look to be a more aggressive or confusing insect than it truly is.
While we take a walk in late July looking for various butterflies, most of us would seek colorful insects fluttering through the fields, but as often happens with nature, there's more to see. Several drab butterflies may be found in the woods at this time, too.
Larry Weber is author of the "Backyard Almanac" and "Butterflies of the Northwoods." He lives in Carlton County and teaches natural science at Duluth's Marshall School.
