Found here nectaring on a flower head of Mojave Thistle (
Cirsium mohavense). Nearby were many clumps of
Asclepias fascicularis, which is among the milkweed host plant species listed in Scott
(1) for
Danaus gilippus.
Note the diagnostic white spots in the brown-orange portion of the forewing (lacking in monarchs).
This can be seen to be a male from the small, elongate marking (usually appearing black, but with much white glistening in the photo) visible here on the left hind wing near the far end of the abdomen. This structure is called a "wing-pocket gland" in Scott
(1) (
cf. "
androconium"). It produces an aphrodisiac pheromone called danaidone which the male Queen synthesizes from pyrrolizidine alkaloids ingested while nectaring on heliotropes or other plants. The widespread
Heliotropium curassavicum may
grow in the area.
The male Queen has an eversible pencil (i.e. cluster) of hairs within the tip of its abdomen which, before courtship, it brushes against the wing-pocket glands to sop up the danaidone aphrodisiac. It then wafts the hair-pencil in front of a female Queen's antennae to induce mating. Read all about it on
pg. 232 of Scott(1). [Note: Scott uses the abbreviation "uph" for "upper hind".]
I don't see these so often in CA...though perhaps I would if I spent more time around milkweeds in the eastern desert parts of the state.