Many gardeners strive to grow beautiful, insect-free plants, but as an insect lover, my favorite plants are the ones that always get pest insects. One favorite in my yard is a yellow daisy that becomes infested annually with beautiful red-colored aphids. For good insect viewing it is hard to beat the aphids. Aphids come in a variety of sizes and colors but most have a soft, pear-shaped body up to one-eighth inch long. Common aphid species come in all shades of green as well as black, pink, yellow and the already-mentioned bright red. The one distinguishing characteristic present on all aphids is not always easy to see, but it is there: each aphid has a pair of tubes on the top side of the back end of the abdomen. The tubes are called cornicles and are used to secrete wax and other substances.