Almost incandescent in the soft light of an overcast sky, the remarkable color of this scrub oak apple gall contrasts sharply with the muted greens, grays and browns of the surrounding chaparral.
The gall forms in response to the larvae of the California gall wasp. The gall protects the developing larvae, as well as providing it a source of food.
On the right side of the gall there appears to be a "sun print" of an oak leaf in the red color, where a nearby leaf may have shielded the surface from sunlight.
From today's run on the Backbone Trail in the Santa Monica Mountains, near Saddle Peak.