You are seeing an small example of why the populations of many insects (and some higher animals) go through a boom and bust every few years. In the case of caterpillars, too many eggs were laid on your local milkweeds and only the earliest and most aggressive catperpillars might make it to cocoon stage. In the wild there are huge losses at every stage of the insect life-cycle: Egg, larvae, pupa, adult.

Now in your square mile, those few plants could be an exception and the population as a whole is normal.

Many moths (and a few butterflies) eat a wide variety of plants, you would have to look up the hostplant list for this tussock to get an idea of what the odds are for finding nearby substitute plants. At this time of year they cannot travel far without dehydrating.

This post was edited by larry_gene on Tue, Jul 15, 14 at 23:32