When biology students are in the field or in the laboratory observing common animals or pictures thereof, we would like them to be able to identify some of the differences between, say, a frog and a toad, or a hare and a rabbit. These differences may be anatomical, physiological, behavioral, reproductive, or developmental. This article suggests a way for students at the high school or higher educational levels to learn how to use the Internet to distinguish between some common or well-known animal pairs (such as butterflies and moths). A starter list of online sources of information is provided for distinguishing between 16 such animal pairs.