North American hosts approximately fifty blue butterflies (Polyommatinae), divided into thirteen genera. Generally small in size, most blue butterflies tend to live in limited geographic ranges.
Changing human demographic and development patterns over time placed stress on North American blue butterfly diversity. In fact, of the nineteen different butterfly species listed as either threatened or endangered under the Endangered Species Act, seven of those species are blue butterflies. Habitat destruction, especially as it pertains to the loss of larval plants remains the primary source of the endangered blue butterfly problem. Habitat restoration will ultimately be the answer to maintaining stability in the current population and enabling their numbers to grow.
This small essay celebrates ten terrific blue butterflies, a sufficient number of species and genera to provide an introductory over view of the North American blue butterfly population. It starts with the Pygmy Blue, pictured at the top of the page, the smallest butterfly in the United States.
In the butterfly world, hairstreaks normally get associated with small wing tails.
The tailed blues (Cupido) represent the exception to the rule. The presence of the tail makes for easy genera identification, the counts two species, the Western Tailed-blue (Cupido amyntula) and Eastern Tailed-Blue (Cupido comyntas).
Blue Butterflies: Euphilotes
Physical similarities among Euphilotes species create identification problems abound. Generally the genus divides along Square-Spotted Blue and Dotted Blue groups, often called complexes, because even within groups, slight physical differences are discernible in different geographical regions.
Square-spotted blues are identified by the presence of a connected band of orange on the underside of the hind wing. The orange band on the dotted blues generally is disconnected.
The Pacific Dotted Blue (Euphilotes enoptes), shown above, has a disconnected orange band, along with the large, almost square spots on the fore wing.
Consider the Arrowhead Blue (Glaucopsyche piasus) as one of the most geographically limited blue butterflies.
While unevenly distributed, their range extends throughout higher elevation areas of the West. Despite the limited range, once seen, it is easily identified by its distinct gray and white wing pattern. While unevenly distributed, their range extends throughout higher elevation areas of the West.
Like so many of the blue butterflies, lupines serve as the host plant for the caterpillars.
North American Plebejus
With the exception of the Southeast, North America’s approximately one dozen Plebejus species fly near fields, forests and roadsides.
Boisduval’s Blue (Plebejus icarioides), a common Western butterfly, commonly gets identified by the presences of white spots and black dots on the underside of the wings.
Picture two shows a mating pair, highlighting the wing pattern on both the male and the female.
Acmon Blues (Plebejus acmon) rank as one of the most common West Coast and western US butterflies. They breed from early spring through late fall and therefore their population is stable to high in most of their territory.
The band of orange spots along the outside of the bottom wing is a good starting field identification clue.
The Northern Blue (Plebejus idas), a complex, or group of butterflies, represents about a dozen different North American subspecies
In common with the Melissa Blue, the Great Lakes Northern Blue subspecies are considered endangered or threatened.
Picture five shows a side view of the male with the characteristic dark spots on the wings (smaller on the bottom wing). Both the top and bottom borders of the wings have orange marks. Females show orange spotted, brown wings. Male top wings are blue without the orange marks.
More Blue Butterflies
The Cassius Blue (Leptotes cassius), one of two native Leptotes species, inhabits Southeast grasslands.
Smaller than average for a blue, with two brightly colored eye spots on the wing’s edge, their quick and erratic flight pattern provides the first field identification clue of its presence.
The Larvae feed on a variety of plants including members of the pea and leadwort families. Adults nectar on a variety of flowers.
The Melissa Blue Butterfly (Lycaeides melissa), a fairly common western species, also has an endangered subspecies relative, the Karner Blue of the Great Lakes region.
The picture highlights a side view of a male with the characteristic orange spots along both wing edges.
Apart from the Karner blue, they are a very common western species with a spillover population in the Midwest.
The Larvae enjoy a mutualistic relationship with ants. The ants protect them from predators, and in return they (ants) feed on larvae secretions.
Having a side view picture of a blue butterfly provides for optimal identification. However, for many blue butterflies a top view picture can be sufficient for identification purposes.
The dark spots on the bottom of the wings of the butterfly in the picture suggest it is a Rearkirk’s Blue (Hemiargus isola), primarily a New World tropical butterfly, also inhabits areas along the southern border of the United States.