Several other smaller groups of butterflies are included in the larger family commonly known as the Gossamer-winged butterflies; there are the Blues, the Coppers, Metalmarks and Hairstreaks. Most of these small butterflies are uncommon in Marin gardens; many of them have associations with just one or two species of native plants in specific habitats. There is just one butterfly within the sub-family of Hairstreaks that is often seen in Marin gardens, and that’s the Common, or Gray Hairstreak.
The Gray Hairstreak (Strymon melinus) is easy to spot, even amongst lots of other butterflies because of a distinctive behavior; its wings are folded while it’s sipping nectar, and it rubs its hind wings together steadily as it feeds. On both surfaces of the hind wing, close to the abdomen, is a large black-pupiled red spot, and delicate, highly mobile ‘tails’. The spots are vaguely like eyes, the tails like antennae, and the rubbing sets it all in motion; constituting a ‘false head’ which diverts predators away from the real body. It’s another wonderful example of ‘back to front’ mimicry!
I like to spend a good bit of time in my garden just looking carefully to see what creatures are visiting the plants and flowers. The native Buckwheats (Eriogonum spp.) are now in full bloom in my garden, a little early this summer; and they attract a lot of insects; native bees, hover flies and butterflies all find resources in the hundreds of tiny individual flowers arranged in compound umbels. The smaller umbels are like tight rounded ‘pom-poms’, and there are sometimes hundreds of these small ‘pom-poms’ arranged together to make up the larger umbel. So many tiny flowers, each one with nectar and pollen, make the Buckwheat flowers a very energy efficient resource for insects. Various Buckwheat species produce flowers in shades of yellow, pale pink to deep reddish pink, or white; they all fade to a really attractive reddish-brown color as the seeds set, and the flower umbels persist on the plant right through to the rainy season.
The flowers of St. Catherine’s Lace (Eriogonum giganteum), the largest of the native Buckwheat species, are white, and held in huge compound umbels that can be eight to ten inches or more in diameter! The plant itself can grow to be quite tall, a lot depends on exposure; I have one specimen that is over six feet, and now above the reach of the deer; another that stays at about four feet, and is still caged to protect it from deer browsing.
Gray Hairstreaks are frequently nectaring on my Buckwheats, and look very similar at a glance to the California Hairstreak (Satyrium californica); both are no more than an inch and a half, wingtip to wingtip, and both are a grayish-brown color; but the underwing pattern of the Gray is a series of fine white and red-edged lines, while the pattern on the California Hairstreak is a series of delicate dots.
But the biggest difference – and the reason that the Gray is more common - is that it is highly polyphagus; second only to the Painted Lady in the scope of plants from various genera that it will use as host plants for its larvae. Plants listed in most books as host plants are from the Mallow, Pea and Spurge families; but always with a note that there are probably many other plants used as well since there are multiple generations each year. The adults have even been recorded ovipositing on some non-native plants like Bottlebrush! This little butterfly flies throughout the year, and is often seen in urban and suburban areas, where it visits many different flowers in gardens while seeking nectar.
In sharp contrast, the Californa Hairstreak is strictly a butterfly of riparian ‘bottomlands’; and is now a rare sight in areas where populations used to occur. The only host plants are Valley Oaks (Quercus lobata) and Mountain Mahogany (Cerocarpus betuloides).
The larvae of the Hairstreaks are slug-like creatures, like many of the Lycaenidae, and very different looking than most caterpillars; so when I noticed a creature like that feeding on a Sidalcea, ‘Party Girl’ (Mallow family) I didn’t know what is was, so brought it in to observe closely. It was apparently in a late instar, and quickly formed a pupa; also distinctly different than most other butterfly pupae. It proved to be a Gray Hairstreak !
But when I noticed a similar looking larva feeding on a Buckwheat flower, I assumed it was one of the blues (which often use Buckwheats as host plants) and brought it in to observe and raise on. And I learned something new again; Gray Hairstreaks will sometimes use Eriogonum as a host plant!