Milkweed: biodiversity in miniature

Fall is here, and the resounding echo of acorns bouncing off the roof reminds me that it is the time when most plants are entering the final stage of reproduction before winter arrives. One of these plants that I came across recently was some milkweed on a roadside in Shohola, PA.

Those who know of the milkweed plant probably realize that the monarch butterfly has a close relationship with this plant, but other insects utilize the milkweed as well. One commonly seen caterpillar is the tussock moth, an orange banded caterpillar with tufts of hair growing out from all sides. Another insect is the red milkweed beetle, a red, black-spotted beetle about one half inch long. The tiny milkweed aphid, bright orange in color, can be seen on some plants in large groups.

One common trait of all these insects is that they are brightly colored, as if to advertise to predators: “Don’t eat me.” This rings true, for the milkweed contains cardiac glycoside in its white sap. This is a chemical that can cause the prey item to taste bad and also cause gastric discomfort to any predator that would feed on these insects.