OK, here's one you may never have heard before, and my husband and I are very curious about it.
While rocking on the porch a butterfly landed on a paper I was holding. Several times it released from its butt a golden orb of liquid (urine?) then sucked it up with its proboscis. When i finally had enough of that it flew to my husband's hand and proceeded to do the same thing? What in the world was that about?
Hope you can help.
You’re right, I’ve not been asked this one! I’ll send it on to some lepidopterists that I know and see what they say.
I do know that a butterfly will pee on carrion and fruit/food that hasn’t liquefied enough for it to eat. The pee dissolves the meat/fruit/whatever a bit so they can drink it back up. I’ve never seen it and found your experience fascinating! Were you sweating out in the heat? Could the sweat have dried too much and the butterfly decided to pee to dissolve the salt from sweat to drink it? Butterflies (males) love sweat.
I’ll contact you if I find out more. How fascinating!
Here is a photo of a Pipevine Swallowtail butterfly peeing.
This is Ron ( the husband in question). It was a hot day; I was not sweating noticeably but obviously on a day such as that I had been producing insensible perspiration all afternoon. Dried salt on my skin is pretty much a certainty (invisible but certain). I believe that you have a good explanation here. Why it was doing that on the paper is a mystery in its own right; possibly some salt or salt analogue is used in processing or sizing it? White paper, in case you wondered.
Several chemicals are used in making paper, including clays and bleach. Dried bleach becomes salt. I don't know if the paper you were holding contained any salt, of course. I'm waiting for a reply from someone who may have a more complete answer. Watch here for the update. You have me quite curious ...