Sylvan Hairstreak

Satyrium sylvinus sylvinus

Lepidoptera: Lycaenidae

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Characteristics: Dorsal wing gray-brown, dorsal forewing usually with an orange-brown suffusion. Dorsal hindwing with orange suffusion near tails. Ventral wing off-white in color with darker markings. The species is similar in appearance to the California Hairstreak (Satyrium californica), but sylvinus is much lighter in color ventrally than that species. Forewing length: 15-17 mm.

Habitats, Behavior: This small lycaenid is nearly always associated with willow trees. At Frazier Park (Kern County), it seems to be associated with Black Willow, Salix gooddingii (specimens from that area are S. sylvinus dryope). The Sylvan Hairstreak is not usually taken at flowers, being more often encountered perching on willow or adjacent tree branches. However, I have taken specimens nectaring on Wild Buckwheat (Eriogonum fasciculatum) and milkweed (Asclepias sp.) blossoms in Kern County.

Distribution: Our records are generally from riparian woodland areas in the county. The colony in the San Joaquin Marsh (University of California, Irvine) could be large, if foodplant abundance is any indication. The Hart Park colony (see below) may have been destroyed in the 1969 flood, as I have not been able to duplicate these pre-flood records in recent years.

Flight Period: One brood, late May to late August. Most records are from early July, although at Hart Park (elevation 120 ft.) several were found in late April 1968, an unusually early record.

Larval Foodplant: Unidentified native Willow  (Salix spp).

Other Remarks: This hairstreak can be relatively common in the right areas. Often the adults can be discovered by tapping willow branches which causes them to fly. They usually alight nearby and then can be easily captured or observed.

From Orsak, L. J. (1977). The Butterflies of Orange County, California. Center for Pathobiology Miscellaneous Publication #3. University of California Press, New York. 349pp.

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