Hairstreaks belong to the cosmopolitan family Lycaenidae, which also includes all blues, coppers and metalmarks. Hairstreaks are rather small butterflies, often with taillike extensions or “hairstreaks” on their hindwings. In Washington State there are eighteen species of hairstreaks, but only one in the genus Strymon, a genus better represented in the new world tropics.

Strymon melinus is one of our most common hairstreaks, found throughout Cascadia except near the Pacific Ocean in Washington. The flight period is very long, late March to early October. An extraordinary diversity of larval host plants is used including Trifolium (clover), Sedum (stonecrop), Quercus (oak), Fragaria (strawberry), Humulus (hops), Polygonum (knotweed), Rumex (dock), Lotus (deervetch/trefoil), Vicia (vetch), Salsola (Russian Thistle), Eriogonum (buckwheat), rosaceous plants, corn, beans, mallows and many others. Strymon melinus occurs in many habitats from coastal scrub-heath to eastern Washington shrub-steppe as well as foothill, mountain and subalpine areas, avoiding only thick forests. However, in spite of its amazing adaptation S. melinus is typically found in small numbers, abundant only in low elevation shrub-steppe riparian habitats along major rivers such as the Columbia, Snake and Yakima. Males perch and wait in search of females, mating soon after females eclose. Eggs are laid singly on unopened coiled terminal flower buds or on nearby leaflets. This species is multi-brooded, reproducing as long as host plants and weather permit, with three broods likely in our area.

Wild larvae can be found as late as early September at mid elevations, attesting to the long flight period and multiple broods of this species. Eggs hatch about day 3 post oviposition, and the larvae reach maturity about 24 days post-oviposition. Pupation occurs at about 27 days and adults begin emerging about 37 days post-oviposition. Eggs are laid on flowers or leaves, are well camouflaged or hidden in flower parts and are strongly attached. Egg shells are uneaten except for an escape hole and the larvae immediately seek flowers to feed on if they are present. If flowers are not available the larvae will feed on leaves. Feeding on flowers is the primary behavior but the ability to utilize leaves permits exploitation of multiple hosts and habitats. Leaf-fed larvae may be green throughout development, while those feeding on colored flowers may be brightly colored in a number of different tones, usually matching the plant. Camouflage provided by adopting the color of host plants is an important survival strategy. This species is often associated with ants which provide some level of protection against predators and parasitoids. Pupation occurs in a sheltered location such as a curled leaf. This species has four instars and is generally solitary; the larvae make no nests at any stage and the pupa overwinters. Partly grown wild larvae can be found by beating host plant flowers such as Eriogonum elatum into a hand net in July or August, or by hand-searching flowers of known hosts. Observing female behavior may reveal the preferred host plant at that locality.

The Gray Hairstreak can be confused only with other “tailed” hairstreaks. The dark gray dorsal color with a bright orange spot on each dorsal hindwing make this species unmistakable. If only the ventral side is seen, the large, bright orange double spots on the ventral hindwing are also unmistakable, and the adults additionally have a handsome postmedian band of black spots with contrasting white outer edges. This is one of our largest hairstreaks, although its size may vary considerably.

Photos by Dave Nunnallee

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