Missing caterpillars

For years, a ritual of summer has been looking for caterpillars on the fennel plants in Kathy and Steve's front yard. They are green, black, and white, and eventually make light green chrysalises. After a week or two the chrysalis becomes almost translucent and a damp and crumpled swallowtail butterfly emerges. We have had caterpillars in jars, fed with fennel until they metamorphed into butterflies, and then we would release them and watch them fly away. But mostly we have looked out for the caterpillars, looked for the chrysalises old and new, and kept track of their comings and goings. Every year by August they were plentiful, with young small ones and middle-sized ones and big ones that had assumed the distinctive comma shape, that meant they were about to be encased temporarily in a chrysalis while a miracle happened.

Until this year. Is the heat, or the drought, or global warming? Hungry birds? Habitat loss somewhere else? Whatever the reason, I have not been able to find a single caterpillar on Kathy and Steve's fennel. Every few days I look, and the caterpillars are not there.

Whatever the cause, this seems to me to be a bad sign. I don't know what critical role swallowtail butterflies play in the great scheme of things, but does this mean something really important is not going to happen? Perhaps they will be back next year.

There is that wonderful Ray Bradbury story, "A Sound of Thunder." (Confession: I did not remember the title, but "Ray Bradbury butterfly time travel" typed into Google retrieved what my memory could not.) A time traveler going back into the past is warned not to change anything, and when he comes back to his present, it's not the same as when he left. On the sole of his shoe, he finds a crushed butterfly.

Perhaps they will be back next year.