Suds for a Bug? Net the First Cabbage White and Win a Beer!

A beer for a butterfly? Suds for a bug? 

It's almost time for the Art Shapiro's annual "Beer-for-a-Butterfly" contest that he's sponsored since 1972. The person who finds the first-of-the-year cabbage white butterfly, Pieris rapae, in the three-county area of Yolo, Sacramento and Solano, wins a beer--or its equivalent.

And bragging rights!

Shapiro, UC Davis distinguished professor emeritus, Department of Evolution and Ecology, is retired, but not from his research and not from sponsoring the annual “Beer-for-a-Butterfly” contest.

Beginning Jan. 1, 2024, Shapiro will be collaborating with the Bohart Museum of Entomology, the "dropping off point," for the entries. Bohart curator and collections manager Brennen Dyer will be accepting the entries. 

Shapiro launched the contest a half a century ago as part of his scientific research to determine the first flight of the year in the three-county area. His research involves long-term studies of butterfly life cycles and climate change.

Shapiro says P. rapae is emerging earlier and earlier as the regional climate has warmed. "Since 1972, the first flight of the cabbage white butterfly has varied from Jan. 1 to Feb. 22, averaging about Jan. 20."

Shapiro, who maintains a research website at, says the point of the contest "is to get the earliest possible flight date for statistical purposes. The rules require that the animal be captured and brought in alive to be verified. That way no one can falsely claim to have seen one or misidentify something else as a cabbage white."

The contest rules include:

  • It must be an adult (no caterpillars or pupae) and be captured outdoors.
  • It must be brought in alive to the Bohart Museum of Entomology, located in Room 1124, Academic Surge Building, 455 Crocker Lane, UC Davis campus,  during work hours, from 8 a.m. to noon, and from 1 to 5 p.m., Monday through Friday. It must include full data (exact time, date and location of the capture) and the contact information of the collector (address, phone number and/or e-mail.) Brennen Dyer will certify that it is alive and refrigerate it. (If it's collected on a weekend or holiday, it can be kept in the refrigerator for a few days--do not freeze it, Shapiro says.)
  • Shapiro is the sole judge.

First of 2023. Shapiro spotted the first butterfly of the year in 2023 at 11:22 a.m., in West Sacramento, Yolo County. He did not collect the butterfly but recorded it as the first of the year. No one came forth with any other. 

Feb 8 was "the 11th latest first rapae day since 1972,” he said, detailing the 10 later finds: Feb. 26, 1972 (“which is probably too late, since I hadn't yet learned where to look for them first!”); Feb. 22, 1992 (“I fully believe that one”); Feb. 18, 1978 and 1986; Feb. 17, 1979; Feb. 16, 1975; Feb. 14, 1981; Feb. 13, 1983 and 1985; and Feb. 10, 1980. “Note that most of these are from the '80s,” he said. “There has indeed been a trend to earlier emergence, though this year is an outlier!”

Shapiro says P. rapae inhabits vacant lots, fields and gardens where its host plants, weedy mustards, grow. The male is white. The female is often slightly buffy; the "underside of the hindwing and apex of the forewing may be distinctly yellow and normally have a gray cast,” Shapiro said. “The black dots and apical spot on the upperside tend to be faint or even to disappear really early in the season.” 

Shapiro, who monitors butterfly populations in the field for more than 200 days of the year,  participates in his own contest. He has been defeated only four times and those were by UC Davis graduate students. Adam Porter won in 1983; Sherri Graves and Rick VanBuskirk each won in the late 1990s; and Jacob Montgomery in 2016. The first three were his own graduate students.

Shapiro nets many of the winners in mustard patches near railroad tracks in West Sacramento, Yolo County

Recent Beer-for-a-Butterfly Contest statistics:

  • 2023: Art Shapiro recorded the first butterfly of the year at 11:22 a.m., Feb 8 in West Sacramento County, Yolo County. He did not collect the specimen and no one can forth with a winner. 
  • 2022: No official contest due to the COVID pandemic, but Shapiro recorded his first-of-the-year P. rapae at 1:25 p.m. on Jan. 19 in West Sacramento, Yolo County
  • 2021:  No official contest due to the COVID pandemic, but Shapiro collected his first-of-the-year at 1:55 p.m. Jan. 16 on the UC Davis campus, Yolo County
  • 2020: Technically, no winner, as Shapiro did not collect the one he spotted in Winters, Yolo County at 11:16 a.m. on Jan. 30 at the Putah Creek Nature Park.  "It flew back and forth across Putah Creek and then departed the area, flying out of reach above the trees," he noted. He waited around for 90 minutes to see if it would return. It did not.
  • 2019: Shapiro collected the first cabbage white butterfly near the Suisun Yacht Club, Suisun City, Solano County, at 1:12 p.m., Friday, Jan. 25. "It was the earliest recorded in Suisun City in 47 seasons."
  • 2018: Art Shapiro collected the winner in West Sacramento
  • 2017: Jan. 19: Art Shapiro collected the winner on the UC Davis campus
  • 2016: Jan. 16: Jacob Montgomery collected the winner in west Davis
  • 2015: Jan. 26:  Shapiro collected the winner in West Sacramento
  • 2014: Jan. 14:  Shapiro collected the winner in West Sacramento
  • 2013: Jan. 21:  Shapiro collected the winner in West Sacramento
  • 2012: Jan. 8:   Shapiro collected the winner in West Sacramento
  • 2011: Jan. 31:  Shapiro collected the winner in Suisun
  • 2010: Jan. 27:  Shapiro collected the winner in West Sacramento

A fellow of the American Association for the Advancement of Science, the Royal Entomological Society and the California Academy of Sciences,   Shapiro is the author of A Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions, illustrated by Tim Manolis and published in 2007 by the University of California Press.

Collaborating with Shapiro on butterfly research projects is Foundation Professor Matthew Forister, the Trevor J. McMinn Endowed Research Professor in Biology, University of Nevada. Forister received his doctorate from UC Davis, studying with Shapiro, his major professor.

Pest of Cole Crops. As a caterpillar, the insect is a pest of cole crops such as cabbage. UC Statewide Integrated Pest Management Program (UC IPM) says the cabbageworm is active throughout the year in California. "Cabbageworm larvae chew large, irregular holes in leaves, bore into heads, and drop greenish brown fecal pellets that may contaminate the marketed product. Seedlings may be damaged, but most losses are due to damage to marketed parts of the plant," according to the UC IPM website.

The Bohart Museum of Entomology is directed by UC Davis distinguished professor Lynn Kimsey. Entomologist Jeff Smith curates the Lepidoptera collection, a global collection of some 500,000 moths and butterflies.