Silvery Blue Butterflies

My home and garden are situated next to an open meadow, and within that meadow grows lots and lots of vetch! The vetch (vicia spp.) also shows up at the edges of my cultivated areas, but early on, while the plants are still small I pull some of it.

There are two species of vetch commonly seen along roadsides, fields and idle lands: hairy or winter vetch (Vicia villosa), and spring or common vetch (Vicia sativa). Both species are native to Europe and were brought to this country to be used as a rotation crop in fields, but have since escaped into wild lands.

On my land, it’s mostly winter vetch that shows up at the wilder edges and grows quickly, draping itself over nearby plants. Without some control it can easily obscure established shrubs. It is an annual plant with stems reaching six feet or more. I pull much of it out of garden areas long before flowers set fruit; there can be ten to fifteen flowers per stem and about four to six seeds per pod, and those seeds have a very hard coat and can persist in the soil in a dormant state for years.

Of course I don’t touch the vetch in the meadow and wild areas of our property, and because it grows here I also see the lovely little Silvery Blue butterflies (Glaucopsyche lygdamus) about this time of year. The top wings of males are a brilliant sky blue; the females usually have dull gray top wings, sometimes with a few bluish scales. The top wings of both sexes display a white fringe next to a fainter black edge, and the underwings are whitish with grayish dots and dashes in patterns that are often variable in individual specimens.

I’ve never seen lots of them at any one time but when I do see them it’s always around vetch. The Silvery Blues used to use California native perennial pea family plants such as the woodland pea (Lathyrus vestitus), false lupine (Thermopsis macrophylla), and sometimes shrubby lupines. Now the species has adapted to the annual exotic vetches, with courtship, mating and ovipositing all take place around the flowers.

Males patrol the patches of vetch, and they also like to follow trails and trodden pathways, maybe because they are devout “puddlers.” In our clay soils, there are often puddles that remain long after the rains. In the species of butterflies that engage in this puddling behavior, it is most frequently the males, and it is believed that they are picking up nutrients that are important for sexual reproduction.

This little butterfly is out and about for just a few months each year—February to about June in coastal areas, and March to May in more inland areas. The males search out the females to mate, eggs are laid, larvae hatch out and develop quickly while feeding on flowers and immature fruits, and then they pupate. The pupae then remain quiescent for about nine months, until the next generation emerges and starts the whole process again.

One of the most fascinating things about a number of the gossamer winged species of butterflies is their association with ants; more on this later!