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Tuesday, August 22, 2017
One morning in mid-July I found a surprise in my herb garden. My lovely borage (see my post on borage) had been turned into lunch by some hungry lepidopteran larvae (caterpillars). The leaves looked like crochet, and clumps of webbing and frass (caterpillar excrement) perched in the tops of several stalks.
While many gardeners would have been upset by this destruction, I had reason to be excited. I knew that many butterflies use herbs as larval host plants, so my co-worker Maggie and I decided to capture and rear a caterpillar to find out what species had come to visit my garden.
The captured culprit was colored in light and dark green, and was covered with spines. Three pairs of true legs and five pairs of prolegs (the pseudo-legs on the back half of a caterpillar) rippled like "the wave" as the caterpillar crawled along the inside of its new mesh enclosure. It ignored the borage stalk I placed in the enclosure with it, persisting in a restless clamber across the mesh top of the butterfly house. I worried that the stress of capture was preventing the caterpillar from eating, and hoped it would settle down.
The next morning I was met by yet another surprise. The caterpillar had formed its chrysalis overnight! (No wonder it was busy crawling along the top of the cage the day before.) The chrysalis was a dark army green with touches of gold highlighting a twin row of spines. I was already one step closer to learning the identity of my mystery guest.
Unfortunately, as nature would have it, I went on vacation the next week and missed the day when the butterfly emerged. Maggie released the butterfly and managed to capture a couple of picture for me.
Based upon all of the clues we gathered (the host plant, the webbing that the caterpillar made, the appearance of the caterpillar, chrysalis, and adult butterfly, and the length of time between chrysalis formation and emergence) I determined that my visitor was a painted lady, Vanessa cardui.
According to the Iowa State University Red Admiral and Painted Lady Research Site, Vanessa cardui is the most widely distributed butterfly species in the world. It is found throughout Europe, Asia, Africa, North and Central America. The host plant range for the species includes Compositae (especially thistles), Boraginaceae (borage!), Malvaceae (especially hollyhock and common mallow), and Fabaceae (legumes like soybean). With its wide host plant range and regional distribution, it is likely that there are painted lady butterflies in your neighborhood too!
I had such fun with this butterfly identification project. I hope it inspires you to plant a little extra in your garden for guests like the painted lady butterfly and other pollinators. For more information about growing gardens to attract pollinators, visit the University of Illinois Extension "Pollinator Pocket" website http://web.extension.illinois.edu/cfiv/pollinators/ or refer to the Pollinator Partnership ecoregion planting guides http://pollinator.org/guides.