In between the rain and the cold, UC Davis Distinguished Professor Art Shapiro of the Department of Evolution and Ecology has been searching in vain for the first white cabbage butterfly (Pieris rapae) of the year.
He participates in his annual “Beer for a Butterfly” contest that he's sponsored since 1972 as part of his scientific research to determine the butterfly's “first” flight of the year — or the first to be witnessed in his contest — in Sacramento, Yolo or Solano counties. The rules: Net the butterfly and win a pitcher of beer or its equivalent. Suds for a bug.
Wednesday (Feb. 8) proved to be a “bingo” day.
“I knew when I left the house at 10:10 this morning that today would be rapae day,” he announced in an email with the subject line, “Bingo!”
He spotted his first rapae of the year, a female, at 11:22 a.m. in West Sacramento, Yolo County. At 11:38, he saw a male. “Both were typical late winter phenotypes, quite different from what was flying in December,” he noted. “My last in West Sac was Christmas Eve. So the rapae-less hiatus was 45 days, i.e. just over six weeks.”
It was 64 degrees, clear, no wind.
“I did not get a specimen,” Shapiro related. “Both of them were flying up near the railroad track at the top of the railroad embankment, where the ground is strewn with coarse gravel. That makes for a warm layer of air in full sun, but terrible footing. I am no longer so nimble or so self-confident as I used to be, and I never got a clean shot at either bug even though I got within about 6 feet of both.”
“I could have stayed in that area and probably eventually would have caught one or both of them,” Shapiro added. “I had to weigh that against covering the rest of the upland half of my site and possibly finding something else out. Remember that the butterfly-friendly window of time each day is still very short. I opted to keep moving, ultimately observing two atalanta (Vanessa atalanta, the red admiral) but nothing else. Malvella (mallow family) has not broken ground yet. Plenty of Erodium (family Geraniaceae) in bloom now, though.
“So for the day, two species, four bugs.”
The find is now in his records. “Today is the 11th latest first rapae day since 1972,” he said, detailing the 10 later finds, starting with the latest: 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!”
“Given how late it is, even though I did not catch a rapae myself, I will offer beer to anyone who does get one and bring it in alive by 5 p.m. this Friday (Feb. 10), and after that declare the contest closed.”
The rules state that the butterfly must be brought in alive to the Department of Evolution and Ecology office, 2320 Storer Hall, during work hours, 8 a.m. to 5 p.m., Monday through Friday, with the full data (exact time, date and location of the capture) and the contact information of the collector (address, phone number and/or e-mail.)
P. rapae is emerging earlier and earlier as the regional climate has warmed, said Shapiro, who has monitored the butterfly populations of central California since 1972 and maintains a research website, Art’s Butterfly World. It's all part of his long-term studies of butterfly life cycles and climate change. Since 1972, he said, the first flight of the cabbage white butterfly has varied from Jan. 1 to Feb. 26, averaging about Jan. 20.
P. rapae inhabits vacant lots, fields and gardens where its host plants, weedy mustards, grow. In its caterpillar stage, it is a pest commonly called cabbageworm that chews on cole crops.
Shapiro, who is in the field 200 days of the year, 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.
Kathy Keatley Garvey is a communications specialist in the Department of Entomology and Nematology, and can be reached by email or phone, 530-754-6894.