Chock one up to...organic gardening?
...letting nature take the lead?
...all of the above?
About a month ago I noticed a bunch of skeletonized leaves on my 2 young Echinacea plants, which I blogged about here and here. It turned out that the leaves were being eaten by checkerspot caterpillars and, by the time I figured out what they were, their numbers had decreased fairly significantly.
Based on what I observed and learned during this brief incident, the caterpillars were eaten by cardinals, eaten by wheel bug nymphs, and probably dispersed to other plants through their natural life cycle. (Note: I haven't noticed damage on any nearby plants, so if they dispersed, they didn't do any damage that I've noted.)
I thought you might be interested in what the little Echinacea ('Sundown'), shown in my first blog on the subject, looks like now. It has 2 blooms, easy to see in the photo, and another 3 healthy flower buds. You can see the shredded leaves still, but there have been many more healthy leaves added. All in all, the plant looks healthy and happy and is a real asset in our entry garden. It's growing bigger by the day. Predator populations are thriving. I have no idea how many, if any, caterpillars survived and whether they've turned into checkerspot butterflies, but a few certainly could have.
Cost of insecticide: $0
Hours of shopping, driving, and spraying: 0
End result: Priceless.