Loranthomitoura spinetorum spinetorum

Thicket Hairstreak

This rarely-encountered butterfly is distinguished by the bold white line on the reddish-brown undersides, and by the flashing blue of the dorsal side seen as it flies. It uses dwarf mistletoes that grow on pine trees as its host, and thus is only likely to be found in pine forests taking nectar at flowers. I got my first photos in June, 2017, after many attempts over many years (mostly in known locales in the San Gabriels or Lagunas). Of course, when I did finally see it, I was southeast of Big Bear where I was looking for something else, but there it was on a blooming ceanothus bush swarming with bees, moths and siva hairstreaks. You'd think it would be possible to confuse it with the latter; however, that dramatic white line against the deep reddish-brown ground color makes identification easy.

Dwarf mistletoe species in our area include Arceuthobium campylopodum and Arceuthobium divericatum. Spinetorum is said to fly from March to August in one or two broods, but June seems to be prime time for them in our mountains.

Photograph of Loranthomitoura spinetorum spinetorum, the Thicket Hairstreak butterfly, near Big Bear
I found this Loranthomitoura spinetorum taking nectar on a ceanothus shrub a couple of miles down Wildhorse Meadows Road (accessed from the Sugarloaf trailhead to the north). June 2, 2017.
Photograph of Loranthomitoura spinetorum spinetorum, the Thicket Hairstreak butterfly, near Big Bear
I found this one along the Sugarloaf Trail in Big Bear, not that far from the one above. It was mostly mud puddling, but here it went for nectar, which made for a better photo backdrop. June 14, 2020.
Photograph of Loranthomitoura spinetorum spinetorum, the Thicket Hairstreak butterfly, near Big Bear
A few weeks later, I came upon this one in Wildhorse Meadow, just south of Sugarloaf, so this was the third time I've seen these in this area. July 8, 2020.
Photograph of Arceuthobium, Dwarf Mistletoe, host plant of Loranthomitoura spinetorum, the Thicket Hairstreak butterfly
This is host dwarf mistletoe - a species of Arceuthobium - on a pine tree. From Mt. Diablo near Walnut Creek, California, June 9, 2017.
Photograph of Arceuthobium, Dwarf Mistletoe, host plant of Loranthomitoura spinetorum, the Thicket Hairstreak butterfly
A closer look at Dwarf Mistletoe from the same hike.

©Dennis Walker