This is one topic that I never imagined I would be writing about. The behavior I witnessed seemed like it must have been something more than the simple call of nature. I watched an Eastern Tiger Swallowtail (Papilio glaucus) expel copious amounts of fluid on the ground in a half-hour period. That I could actually see the butterfly doing this is a tribute to my telephoto lens.

This butterfly expelled so much fluid that I wondered if the poor creature was sick. After doing a little research¹, it seemed plausible that that this butterfly had emerged from its chrysalis, or was consuming salts and minerals from the mud.

This butterfly could fly, and did fly off – but not far. I watched as he flew to a perch in a nearby tree and eventually returned to the muddy area where I was standing. It was a hot day near the end of July, in the Fort Worth Nature Center off the banks of the West Fork of the Trinity River. I’ve read in several sources that butterflies expel excess fluid shortly after emerging from their chrysalis. Fluid stored in the body is used to fill-out the wings. Excess fluid is expelled, though often that fluid is dark.

(this is a different individual)

Though I found several sources that mentioned these butterflies’ tendency to consume minerals from mud puddles, I did not find an explicit description of expelling excess water that might be consumed in the process. From the scene I witnessed, I think this is the most likely explanation. The swallowtail spent a LOT of time at the mud puddle, and “peed” out a LOT of fluid.

I’ll close with a couple of pictures of a Giant Swallowtail (Papilio cresphontes) I saw on the same trip. If you’d like to see butterflies around your home, consider planting native plants to feed both the caterpillars and the adult butterflies. These plants are often called “larval host” plants and “nectar” plants. And for goodness sakes, don’t spray pesticides – let those caterpillars munch away on those plants and you may be rewarded with lovely butterflies like these.  Like so many species, habitat loss tops the list of factors contributing to the alarming decline of these and other pollinators. If you would like to learn more about what you can do to help conserve butterflies, please visit the Xerces Society, specializing in invertebrate education and conservation.