Considered a pest for most of the year, California's most common white butterfly flutters at low elevations around vegetable gardens. But on Jan. 1, the European Cabbage Butterfly becomes an object of desire for evolution and ecology professor Arthur Shapiro. In fact, he holds an annual contest for the first live captured Pieris rapae, a "weed" species introduced from Europe. To win, participants must bring a live butterfly to the receptionist in evolution and ecology at 2320 Storer Hall. Butterfly hunters must provide the exact time, date and place of capture. Hint: try cabbage patches, vacant lots and weedy roadsides on Jan. 11, the day Shapiro predicts someone will see the first one of the season. Eligible butterflies must have been captured outdoors in Yolo, Solano or Sacramento counties. "Knowing that people are out there looking is an added spur for me to be out in the field," says Shapiro, who has run the contest for more than 20 years. "It maximizes the pressure to collect accurate data." He uses the data, among other things, to understand how adaptable organisms are to environmental changes and to provide some insight into the species' local evolution.