What's folding my leaves?

Wednesday, December 2, 2015

You might take a close look at some of your plants, in particular those in the legume family Fabaceae. You will probably find some leaves that appear to have been notched, like someone made two cuts at the leaf margin and folded over the resulting tab.

Something lives under this rolled leaf.

In fact, someone has. Peel the little tab back and you may find a small caterpillar, about 1/8" long, and very colorful. It's the larva of the long-tailed skipper, Urbanus proteus. It's a rather non-distinct brownish skipper, but if you can view one with wings open, its back shows a splash of beautiful metallic blue.

The long-tailed skipper prefers to lay its eggs on leguminous plants like peas, beans and many, many others in the huge Fabaceae family. The hatchlings feed on the foliage, eventually folding over a leaf edge and spinning silk within it to pupate within a nice little tent.

Larva of the long-tailed skipper on bean plant

I am not sure they cause much damage, though in the south are considered a crop pest. At Fairchild, I have discovered them on a bean plant in the Edible Garden, but the plant is doing fine. Likewise, my butterfly pea plant, Clitorea ternatea, is harboring dozens if not hundreds of them, and it's nevertheless flourishing.

Left: Clitorea ternatea, butterfly pea, a common host for long-tailed skippers. Right: Eggs of the long-tailed skipper on a bean plant leaf