The annual “Beer for a Butterfly” contest is set to return to the Sacramento, Yolo, and Solano counties. The event, organized by UC Davis Distinguished Professor Emeritus Art Shapiro, invites participants to find and collect the first cabbage white butterfly of the year in these areas. The winner receives a pitcher of beer or its equivalent.
Shapiro has led this contest since 1972 as part of his long-term research on butterfly populations in Central California. According to Shapiro, “the point of the contest is to get the earliest possible flight date for statistical purposes.” He uses this data in his studies on butterfly life cycles and climate change.
The cabbage white butterfly, known scientifically as Pieris rapae, is considered a pest during its larval stage. The UC Statewide Integrated Pest Management Program describes that “cabbageworm larvae chew large, irregular holes in leaves, bore into heads, and drop greenish brown fecal pellets onto edible portions of the leaf.” The larvae are sluggish but feed heavily on vegetables like cabbage, broccoli, cauliflower, kale, Brussels sprouts, collards, and mustard greens.
Eggs are laid singly on leaves and are pale yellow to orange. Larvae grow up to an inch long before pupating attached by silk strands to stems or nearby objects. Pupae are green with faint yellow lines; there is no cocoon. The cabbageworm remains active throughout the year in California.
Adult butterflies have white wings with black dots that may be faint early in the season. Males are white while females can appear slightly buffy. Shapiro notes: “The underside of the hindwing and apex of the forewing may be distinctly yellow and normally have a gray cast…The black dots and apical spot on the upperside tend to be faint or even to disappear really early in the season.”
Habitats include vacant lots, fields, and gardens where host plants from the mustard family grow.
Over more than 50 years of competition, Shapiro himself has won most contests but was bested four times by UC Davis graduate students: Adam Porter (1983), Sherri Graves and Rick VanBuskirk (late 1990s), and Jacob Montgomery (2016).
Recent records show that Shapiro collected winning specimens at various locations across Yolo County:
– In 2025 at 12:13 p.m., Jan. 23 in West Sacramento
– In 2024 at 11:30 a.m., Jan. 29 in West Sacramento
– In 2023 at 11:22 a.m., Feb. 18 in West Sacramento
During pandemic years when no official contest was held (2021–2022), Shapiro continued recording first sightings independently.
Interested participants can contact Art Shapiro at theochila@gmail.com or amshapiro@ucdavis.edu for further information or to report potential winners.
