This is a "Best of Wendy Langhans" Report.
What exactly is a hairpencil? Is it some sort of stick-shaped hair ornament? Nope. Hairpencils are cross between (1) lighting a scented candle and (2) spreading pixie dust with a magic wand. Let me explain.
Entomologists use the word “hairpencil” to describe a brush-like structure on the abdomen of some male butterflies and moths. The word was a translation error, an anglicized version of the German “haarpinsel”, which means artist’s paint brush .
Below is a photograph of a hairpencil found on a Common Indian Crow butterfly, taken by my friend Dr. Paul Levine in Hyderabad, India. It does look a bit like a well-used paintbrush, doesn’t it? Or maybe flashing light coming from the tip of a magic wand?
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According to the MonarchWatch website , “hairpencils are telescoping tubes, or sheaths, that are extended and retracted by the butterfly through fluid pressure and muscle contractions.” Click here  to see their close-up view of an extended hairpencil. Locally, hairpencils can be found in members of the Milkweed butterfly family, which includes our familiar Monarch butterfly (Danaus plexippus), as well as Queen (Danaus gilippus) and Soldier butterflies (Danaus eresimus).
But how do butterflies use their “hairpencils”? To answer this, I first have to describe another characteristic of male Milkweed butterflies - the alar pockets  - “small black pouches” on their dorsal wings, which contain “specialized scales”. Click here  to take a closer look at the alar pouch.
Male Milkweed butterflies, especially the Queen butterfly (Danaus gilippus), dip their hairpencil “brush” into their alar pouch, whose scales absorb chemicals produced by the hairpencil glands. These scented scales are then “wafted” over the antennae of the female butterfly, allowing the pheromones to act as an aphrodisiac. So these butterflies scatter scented pixie-dust-like scales to create a romantic mood, the same way we humans light a scented candle to create the proper ambiance.
So when I said earlier that hairpencils were a cross between a scented candle and a magic wand scattering pixie dust, I wasn’t as crazy as I sounded, right?
To see photos of Queen butterfly courtship and mating behavior, click here .
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Santa Clarita Valley Outdoor Report: Hairpencils