Today, as I was walking out to my truck, I checked the butterfly weed. Sure enough, I spotted a little striped caterpillar, munching away. When I got home, I took a moment to check the whole plant over, and discovered two more, parked underneath a leaf.

These little guys are monarch caterpillars. Each September, they visit any garden that has a milkweed planted in it. I, like hundreds of gardeners, have a milkweed in my garden, not because it’s pretty, because there really are prettier plants, but because it’s the sole food of monarch caterpillars. The butterflies lay their eggs on the milkweeds, and when they hatch, the caterpillars need tons of food to grow. Last year, three of them stripped my full grown butterfly weed completely before they marched off in search of more. I have no doubt this one will be bare by tomorrow.

In years past, milkweeds grew abundantly in Texas, which is the intersection of three of the migratory paths of the monarchs. They generally grew in and around crop lands and pastures, and since they self-seed themselves aggressively, there were plenty for the hungry caterpillars. However, native milkweeds are being killed off by agricultural herbicides, development, and roadside mowing. Without the milkweeds, there are no caterpillars—and eventually, no butterflies.

At some point, I plan to dedicate a section of my backyard garden to monarch habitat. For now, I just have the lone plant, which I’m happy to see is doing exactly what nature intended for it to do.

More information on butterfly gardens and monarch waystations can be found at Monarch Watch.

UPDATE: I’ve just learned that these are actually queen caterpillars rather than monarchs. They look pretty much identical, except for the little feelers—queens have a set in the middle, and monarchs don’t. The butterflies also look very similar.