Spotting the Cabbage White Butterfly

They're everywhere.

But they're not welcome.

Agriculturists who commercially grow cabbage and other cucurbits aren't fond of the cabbage white butterlfy, Pieris rapae, because its larvae are pests that ravish their crops.

No welcome mat for them.

This butterfly, however, is welcome--sort of--starting Jan. 1 of every year in the three-county area of Sacramento, Solano and Yolo. It's the target of the "Beer for a Butterfly Contest," sponsored by Art Shapiro, UC Davis distinguished professor of evolution and ecology. The first one collected in the three-county area collects a pitcher of beer or its equivalent.

Professor Shapiro, who maintains a research website at, launched the contest in 1972 as part of his long-term studies of butterfly life cycles and climate change.  Pieris rapae  is emerging earlier and earlier as the regional climate has warmed, he says.  "The cabbage white is now emerging a week or so earlier on average than it did 30 years ago here."

He usually wins the suds-for-a-bug contest; he has been defeated only four times, and all by UC Davis graduate students. This year (2018) he collected the cabbage white butterfly, Pieris rapae, at 11:23 a.m. Friday, Jan. 19 in one of his frequented sites—a mustard patch by railroad tracks in West Sacramento, Yolo County.  (See Bug Squad blog)

Last weekend we spotted a cabbage white nectaring on lantana, a common occurrence. What was not so common was that this one wasn't skittish. It lingered like a ballerina anticipating a curtain call, and allowed us to photograph it in flight.