The Wonder of Hairstreaks

Standing, talking to a photographer friend and enjoying the beauty of the first sunny day all week, a streak of bright blue darted past my eyes. The color was electric, rivaling the azures of morpho butterflies in the tropics, though this bug was much smaller. Just past our heads, it landed in a patch of late boneset, where we had already been enjoying the butterfly diversity. Now all attention was turned to the new arrival: a Great Purple Hairstreak (Atlides halesus); not a large butterfly, but big for its family, nearly twice the size of some hairstreaks; most are less than an inch tall. This particular species is notoriously uncommon in both Arkansas and elsewhere in its range. One cannot usually go looking for it without failure, they have to find you…like this one did. The Great Purple Hairstreak lays its eggs on mistletoe, which the caterpillars feed on. With the abundance of that particular plant in the Ozark region of Arkansas, one would think the species to be much more common. But, for some reason they aren’t. In fact, this was the only one I’ve ever seen.

Great Purple Hairstreak (Atlides halesus) in all its glory.

Hairstreaks form the diverse subfamily, Theclinae, in the larger family of “gossamerwings” called Lycaenidae. Taking a step backwards to the overarching family Lycaenidae, there is an array of similar species that are nearly equally as enjoyable as the hairstreaks. They have such names that inspire closer investigation like copper, blue, elfin, and azure; but it would take many more words to give them a fair chance! So, onward to hairstreaks…

It’s hard to track down the origin of the name “hairstreak”, but it seems to have begun appearing in literature in the early 18^th century. One of the first mentions is in Gazophylacii naturae et artis decas prima, written by English apothecary James Petiver, who had a penchant for botany and entomology. In this book, with hand-colored plates, the name “hair-streak” appears several times. However, he never explains the reason behind this name. Many of the hairstreaks have tell-tale black antennae ringed with white bands that could have something to do with the moniker.

My Great Purple Hairstreak was seen at a local restored and mitigated wet prairie site. Calling it amazing is an understatement. In less than ten years of restoration work, the 46-acre site functions largely as it did before it was settled in the 1830s. Both flora and fauna have bounced back, including several rare or unusual species thought lost to the area. In late summer and early fall, the prairie abounds with insect diversity, with an emphasis on the butterflies. It was at this same prairie, three days before the Great Purple Hairstreak, that I found another rarity of the same family: White M Hairstreak (Parrhasius m-album). Whoever decided upon this butterfly’s Latin name should get a pat on the back for creativity. The species name literally means “white ‘m’” (Parrhasius was a famous Greek painter in ancient times). This is another large hairstreak with beautiful blue upper wings, a trait exhibited by several other members of the family. However, in almost all species the color remains hidden. Hairstreaks keep their wings held tightly upright, providing quick flashes of the blue only in flight.

White M Hairstreak (Parrhasius m-album)

Sharing boneset with these rarities were two other, more common hairstreaks, both fairly numerous on the property. First, the Gray Hairstreak (Strymon melinus), perhaps North America’s most widespread hairstreak. Whereas most butterflies have a select list of particular host plants, the Gray Hairstreak is known to use a wide variety, lending to it the perfect means for being so common. Nonetheless, it’s good-looking: frosted grays flecked with orange and white.

Gray Hairstreak (Strymon melinus)

Red-banded Hairstreak (Calycopis cecrops)

The other species on this particular prairie is the Red-banded Hairstreak (Calycopis cecrops), a specialty of the southeastern U.S. Unlike most caterpillars, which feed on living host plants, Red-banded Hairstreak caterpillars feed on fallen and decaying leaves of sumac and certain oaks. This is a hairstreak I always look forward to seeing. It flies from April to October, but I seem to find the largest numbers after a final big hatch in late summer. More of a bluish-gray, this tiny butterfly sports the namesake thick orange band, running through both the hind and forewings, accented with an array of black spots and thinner white bands.

Leaving Arkansas and heading south into the Lower Rio Grande Valley of Texas, the Red-banded Hairstreak is replaced by a look-alike: Dusky Blue Groundstreak (Calycopis isobeon). This hairstreak can be found in thornscrub habitat, accompanied by riparian areas throughout southern Texas. Caterpillars of the Dusky Blue Groundstreak find the decaying plant matter they are looking for here, and grow into a butterfly very closely resembling the Red-banded Hairstreak, which doesn’t exist along the Mexican border of far-south Texas. On occasion, where their ranges meet further north, the two species have been known to interbreed, begging the question of whether or not they are actually two distinct species.

Dusky Blue Groundstreak (Calycopis isobeon)

Pondering too deeply about such matters and you could miss another hairstreak in this diverse and underappreciated habitat that dominates south Texas. As usual, a fleeting glimpse of a quick grayish butterfly almost always leads to a hairstreak. In the woods along the Rio Grande, one such quick flyby led to a Mallow Scrub-Hairstreak (Strymon istapa istapa). Arguably the dullest of the bunch so far, this mostly gray-and-white hairstreak, with brown upperparts, makes up for looks with its interesting geographic history. The species is found in two disjunct ranges: one extends from Texas, across the southwest, and into South America; the other from southern Florida, down through the West Indies. Some butterflies have a similarly split range, but its most apparent in my bird-driven world with species like Crested Caracara, Burrowing Owl, and the scrub-jays, which eventually diverged into several species because of the separation.

Mallow Scrub-Hairstreak (Strymon istapa istapa)

Mention of the West Indies brings me to yet another, the Atala Hairstreak (Eumaeus atala). In fact, my preferred hairstreak even after the Great Purple entered into my life. Like the Great Purple, the Atala is classified as one of the “large tropical” hairstreaks; not quite as large, but equally as flashy. Its larvae feed on coontie, a group of plants common in the Caribbean. 

Atala Hairstreak (Eumaeus atala)

In nature, it’s often hard to find a creature that captures the essence of beauty in its entirety. Of course, the definition of beauty is relative, but the Atala is the whole package. For starters, the butterfly is a silky, jet black, something that naturally pleases the human eye. Staring at this bug is like staring into a black hole. As the sun works its way through a patchwork of leaves, light hits tiny scales of aquamarine among the black. Like looking at a field of stars on a moonless night is the Atala. Two constellations of spots, one on the hind wing and one on the body, stand in contrast to the bright orange abdomen and orange-red splotch on the lower hind wing. 

Its host plant, coontie, is a primitive cycad. Several species are found in well-drained, sandy soils of West Indian islands, often in pine woods. It was in one particularly dry pine forest on the island of Abaco, in the Bahamas, that I saw nearly 50 Atala; clearly common when coontie is available. The Atala was probably once common in southern Florida and the Keys, but is now very unpredictable from year-to-year. The preferred habitat for it and its beloved coontie is degraded and nearly gone from the Continental U.S. However, there is some comfort in knowing the species lives on further south.

Deeper into the tropics appears the genus Arawacus. Though a recognizable genus, as with many butterflies in the tropics, it is often hard to identify a species accurately due to lack of study. Arawacus is known for its “zebra striping” in some form or fashion, some livelier than others. A particularly strongly marked species is the Togarna Hairstreak (Arawacus togarna). One of the better known of the genus, this species ranges from southern Mexico through Belize, where I photographed it, and south into Amazonia. Quite different from a standard-issue hairstreak, this butterfly took me completely off guard, as do most things on a naturalist’s first trip to the tropics. Wandering through a break in the jungle, the Togarna streaked (typical) past my face and landed on a blade of grass. I was immediately enamored by its thick black, triangular markings interspersed with creamy lines, all culminating in an attractive orange spot at the end of the hind wing.

Togarna Hairsteak (Arawacus togarna)

But of course, you don’t have to travel far to get your own hairstreak fix. Hairstreaks and their brethren can be enjoyed the world over. There are around 5,500 species in the family Lycaenidae known to exist in almost every corner of the globe, from backyards to the depths of a remote jungle. Amazingly, nearly half of these species, as caterpillars, have formed mutualistic relationships with other insects; most often being tended by ants. “Tended” has a variety of different meanings, but in most cases, the caterpillar secretes a sugary liquid that the ants consume. Because of this important resource, the ants keep constant guard over their caterpillar herd.

The tending can get pretty extreme. Eastwood & King (1998) studied the relationships of several ant and hairstreak species on an acacia tree in Australia. One caterpillar, (Arhopala wildei), feeds on the tree, which is tended by a very aggressive ant (Oecophylla smaragdina) who enjoys the sap produced by the tree. The ants are ruthless protectors, yet somehow the caterpillars survive. On the same tree, there’s another ant (Polyrhachis queenslandica) that shuts itself away from the aggressive ants in protected shelters during the day. The A. wildei caterpillars live in these compounds with the ants and are carried out at night to feed when the aggressive species of ant is inactive. The benefit to the ants is, as usual, a sugary secretion. On the flip side of the same story, the aggressive O. smaragdina ant is associated with its own Lycaenid caterpillar (Liphrya brassolis). However, this species feeds on the ants, who gain nothing, not even a chance to counterattack due to the caterpillars’ thick skin. This is a complicated example, but just awesome!

Here's a simpler North American example of an ant waiting for the sweet secretion from a Gray Hairstreak caterpillar. Hobbs State Park, Benton County, AR

"I believe that there is a subtle magnetism in nature,which if we unconsciously yield to it will direct us aright."--Henry David Thoreau, Excursions, 1863

For further reading: Caterpillars of Eastern North America by David L. Wagner, A Swift Guide to Butterflies of North America by Jeffrey Glassberg, Arkansas Butterflies and Moths by Lori A. Spencer