http://stream.publicbroadcasting.net/production/mp3/knau/local-knau-698427.mp3
Flagstaff, AZ – Earth Notes: Hilltopping Butterflies
It's easy to see butterflies. They're big, colorful, and conspicuous. But consider how they might see each other. Those tiny insect eyes don't produce very good vision, making it extremely difficult for butterflies to stumble across suitable mates. Imagine trying to find someone a mile off when you can't see details even a few feet away!
As a result, butterflies have come up with an ingenious system that improves the odds of finding each other. They all head uphill.
Hilltopping is a straightforward and elegant solution that doesn't require complex decision-making or dialogue. Simply head uphill and at some point you'll run into a bunch of other butterflies doing the same thing.
Once they're at a high point, males start doing what bachelors tend to do. They show off to each other. They strut their stuff for females. In turn, females head uphill when they're ready to mate, then quickly return downslope to lay eggs on the host plants they like.
You can watch hilltopping in spring and summer on almost any high point in the landscape. It's especially impressive when you climb a hill and encounter large numbers of showy butterflies, like swallowtails or great purple hairstreaks, perching on rocks and bushes or chasing back and forth in small groups.
If you start looking closely you may even see other types of insects doing the same thing on a hilltop putting into practice a workable solution to that common challenge of finding a mate.
-David Lukas