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Creek Running North
October 25, 2005
Sex and drugs
I'm always on the lookout for butterflies when I'm in the desert. For one thing, they're cool. For another, there's always the chance that a large butterfly flitting in my peripheral vision will turn out to be a yucca giant-skipper, whose larvae bore into the trunks of Joshua trees, often killing them. Precious little research has been done into Megathymus yuccae, and as the animal is one of the J-tree's few insect pests, I feel I really ought to observe its behavior, a pursuit in which I have so far been unsuccessful.
The butterfly pictured here is not a yucca giant-skipper. It's a queen butterfly, a reasonably close relative of the famous monarch. It's feeding on a yellow composite flower that I forgot to identify, and I'm having trouble ding so from the photos. Machaeranthera? Baileya? Viguiera? Some sunflowery thing, anyway. This butterfly is, I think, a female, though neither my photos nor my memory are conclusive here.
Queen butterflies (Danaus gilippus) are pretty dang common even outside the Mojave, so much more research has been done on them. They're odd. Male queens spend much of their adult lives feeding on milkweeds and other such mildly toxic plants, and collect the plant toxins - pyrrolidizine alkaloids, for the most part - for later use in mating. The males metabolize some of the alkaloids into sex pheromones, notably 2,3-Dihydro-7-methyl-1H-pyrrolizin-1-one (a.k.a. danaidone).
On the other hand, some of the collected alkaloids remain more or less chemically intact. After mating, those alkaloids are incorporated into the eggs, protecting them (it is thought) from predators. But for eggs to be produced, mating must occur. For mating to occur, males and receptive females must find one another. Danaidone serves as the conveyer of intent: in the elegant parlance of the bug sex geeks, it's a semiochemical. Male queens carry danaidone in small pockets on their hindwings. When they find a female, the males use two small specialized appendages on their abdomens - called "hairpencils" - to remove some of the danaidone from the pockets, then smear it on the female's antennae.
It is suspected - at the risk of ascribing volition to beings with approximately the mentative power of a flashlight - that females may preferentially look for males with huge amounts of danaidone, which likely corresponds with a good stash of egg-protecting pyrrolidizine alkaloids. Males with the readiest supply of drugs get the nod, making the female queen butterfly sort of the crack whore of the insect world. Of course in the butterfly's case, she's doing it for the children.
This female was remarkably patient with my camera-wielding. As she fed, a ceraunus blue resisted my efforts to immortalize it as it drank from a shrinking patch of mud, and the probable southern dogface feeding on the mesquites in the wash the next day didn't let me come anywhere near it.
Posted by Chris Clarke at October 25, 2005 04:42 PM
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Males with the readiest supply of drugs get the nod, making the female queen butterfly sort of the crack whore of the insect world. Of course in the butterfly's case, she's doing it for the children.
Thanks for the laugh, I needed it.
the southern dogface in closed-wing position looks a lot like a clouded sulphur, down to the spot mid-wing.
I'm just amateur at this ID stuff, but is the difference in the wing shape? the sulphurs seem to have more rounded upper wings - ? or is it more the range that defines them?Posted by: peacebug at October 26, 2005 10:37 AM
heh heh -- You said "hairpencil." heh heh heh
Sorry. That was my inner "bug sex geek." Every artist has one -- or didn't you know?Posted by: Sara at October 26, 2005 12:21 PM
Peacebug: It's range. Not a lot of clouded sulphurs in that part of the Mojave (at least according to Kaufman).Posted by: Chris Clarke at October 26, 2005 08:11 PM