Satyrium dryope desertorum

Sylvan Hairstreak

This species flies from approximately May to August in a single brood in habitats where the host willows thrive. In Allen, Brock, and Glassberg's Caterpillars in the Field and Garden, they say (p.56) the larvae can be found from April to July, and the eggs hatch as the willow buds appear. A 2022 paper found that populations of Satyrium sylvinus from the northwest and the southeast were as different from each other as they were from S. californica. Therefore, they split sylvinus into two, with dryope moving from subspecies status to a full species to represent the southern group. Subspecies desertorum should - I believe - cover the southern California sylvan hairstreaks.

The type locality of desertorum - Oak Creek - is in the Tehachapis a few miles west of the town of Mojave. The Pacific Crest Trail runs along Oak Creek for several miles. It would have looked very different in 1905 when the types were collected; today the ridgeline is dominated by wind turbines.

Photograph of Satyrium sylvinus desertorum - Sylvan Hairstreak
A Sylvan Hairstreak along the West Fork trail in the San Gabriel Mountains. June 1, 2007.
Photograph of Satyrium sylvinus desertorum - a Sylvan Hairstreak butterfly
Satyrium sylvinus desertorum at Upper Newport Bay, Orange Co. June 18, 2007.
Photograph of Satyrium sylvinus desertorum - a Sylvan Hairstreak butterfly
This is the original description by Fordyce Grinnell of Satyrium sylvinus desertorum. It was published in 1917 in a journal from the University of Toronto called The Canadian Entomologist. Grinnell was president of the Entomological Club in Pasadena, and he organized the Lorquin Club, which in 1927 changed its name to the Lorquin Entomological Society.

©Dennis Walker