It's the skippers that tend to vex people setting out to learn our lepidopterans. Skippers are small and often inconspicuously brown, often behave more mothlike than butterflylike, and the species can be confusingly similar.
Not so the bold and pugnacious Silver-spotted Skipper, seen above nectaring on Swamp Thistle, Cirsium muticum. A jumbo in the world of skippers, the flashy Silver-spot is probably the first skipper many people learn, and the most widely recognized of its ilk.
Well, the Silver-spotted Skipper and every other butterfly and moth was a caterpillar before they transformed into the beautiful and much more obvious flying machines that we see flitting about. Voracious plant-eating machines, these cats are adept at hiding and not often seen. It behooves these tasty little bags of protein to remain in hiding during the day, when birds and all manner of other predators who would love to make a snack of them are out and about.
But, the trained eye can still find caterpillars. In the case of the Silver-spotted Skipper, watch the foliage of its favorite host plant in these parts, the Black Locust, Robinia pseudoacacia. Should you see a series of leaflets pulled over and sewn together with silk, you're liable to have an SS Skipper larva.
The little oblong white cases are the coccoons of a braconid wasp, which are common parasitoids of caterpillars. If the adult wasps locate a suitable caterpillar, they'll either lay their eggs on the unwilling host or inject them into its tissue. When the eggs hatch, the tiny wasp grubs burrow happily through the caterpillar's tissue, consuming all of the non-vital stuff. Finally, in a last hurrah, the grubs finish off the victim in a fatal feeding frenzy and burst from the victim to pupate, as seen above.
With threats like that lurking around every leaf, I'd hide too.