A Scientist Hypothesizes That the Larvae of a Particular Species

Essay

A scientist hypothesizes that the larvae of a particular species of swallowtail butterfly uses olfaction (the sense of smell) to locate their preferred host plants in the carrot family. To test the hypothesis, the scientist uses extracts from various plants-including some from the carrot family-to moisten small pieces of paper arranged randomly under a wire screen. Swallowtail larvae are released on the wire screen but cannot come into direct physical contact with the pieces of paper. What is the advantage of this experiment compared with simply presenting the larvae with a choice among various plants?