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 in the three-county area of Sacramento, Yolo and Solano. The rules: net the first butterfly and win a pitcher of beer or its equivalent. Suds for a bug.

Today, 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! 

"It was."

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 6 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, 2 species, 4 bugs."

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.

UC Davis distinguished professor Art Shapiro's annual Beer-for-a-Butterfly Contest, in which he trades a pitcher of beer (or its equivalent) for the first-of-the-year cabbage white butterfly collected in a three-county area, is of special interest this year. 

“It's of special interest this year because as of a few days ago the bug was still flying and laying eggs, which will result in non-diapause pupae,” said Shapiro, a noted butterfly expert who researches biological responses to climate change. “Depending on the weather, that could mean an earlier-than-usual emergence. There is even a slight chance the fall brood is not over yet...”

Shapiro, a member of the Department of Evolution and Ecology faculty, has sponsored the “Suds for a Bug” contest since 1972 to determine the Pieris rapae's first flight of the year in the three-county area of Sacramento, Solano and Yolo. He launched the contest as part of his long-term studies of butterfly life cycles and climate change. 

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

Shapiro, who has monitored butterfly populations of central California since 1972 and maintains a research website at http://butterfly.ucdavis.edu/, 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 Department of Evolution and Ecology office, 2320 Storer Hall, UC Davis, 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.) The receptionist 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 is the sole judge.

The professor said 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,  usually wins the 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.

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

Recent Beer-for-a-Butterfly Contest statistics:

• 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

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

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.

Related Link:
Research Publication on Non-Diapause Overwintering Cabbage White Butterfly and Anise Swallowtail
Non-Diapause Overwintering by Pieris rapae (Lepidoptera: Pieridae) and Papilio zelicaon (Lepidoptera: Papilionidae) in California: Adaptiveness of Type III Diapause-Induction Curves by Art Shapiro, published in 1984 in Psyche: A Journal of Entomology (open access article)

First paragraph: "Diapause is generally regarded as a physiological adaptation which increases the probability of surviving the adverse season, and thus of reproducing after it is over. Many insect species show geographic differences in the environmental regimes which induce or inhibit diapause (e.g., critical photoperiod) and in the strength of the diapause induced. Such interpopulational differences are commonly viewed as "fine tuning" to local climates, accomplished by natural selection and reflecting a genetic basis (e.g., Istock, 1981). Intrapopulational differences in photoperiodic sensitivity and diapause strength (e.g., chilling requirement) also occur, and have been interpreted as polymorphisms which "spread the risk" of environmental uncertainty over the population (cf. Bradshaw 1973, Shapiro 1979, 1980a). In multivoltine insects in seasonal climates, offspring produced by the last seasonal generation of adults are commonly induced to enter diapause by specific combinations of environmental factors; in mid-latitudes these are likely to be decreasing photophase/increasing scotophase and decreasing or consistently low night temperatures. Warmer nights tend to shorten the critical photoperiod for a given population, or may effectively inhibit diapause altogether under field conditions." (See more) 

It's Sept. 4, 2019. We notice a monarch butterfly laying eggs on milkweed in an enclosed Vacaville retail nursery. We purchase the plant and add it to our pollinator garden.  Did the eggs ever hatch? Did we ever get caterpillars, chrysalids and adults?  No. Zero. Zilch. Nada.

Why? Hypothesis: the milkweed may have been treated with pesticides before it was shipped to the nursery.

Newly published research led by scientists at the University of Nevada, Reno (UNR), in collaboration with the Xerces Society for Invertebrate Conservation--and appearing in the peer-reviewed science journal Biological Conservation--sheds some light on pesticide contamination of milkweed plants being sold in retail nurseries across the United States.

The article, titled "Milkweed Plants Bought at Nurseries May Expose Monarch Caterpillars to Harmful Pesticide Residues," indicates that every single plant tested in stores across the nation--every single one!--contained multiple pesticides, "even those that were labeled 'wildlife-friendly," according to the researchers, who included co-author Matt Forister, a UNR biology professor.

The team collected leaf samples from 235 milkweed plants purchased at 33 retail nurseries across the United States to screen for pesticides. "Across all samples, we detected 61 different pesticides with an average of 12.2  compounds per plant," they wrote in their abstract. "While only 9 of these compounds have been experimentally tested on monarch caterpillars, 38% of samples contained a pesticide above a concentration shown to have a sub-lethal effect for monarchs."

More than one third of samples contained a pesticide at a known harmful concentration for monarchs.  Those pesticides included neonicotinoids (neonics).

"In a previous study in California that primarily looked at milkweed in agriculture and urban interfaces, we had looked at a small number of plants from retail nurseries, and found that they contained pesticide but it was surprising to see the great diversity of pesticides found in these plants," Forister told Mike Wolterbeek in a Nevada Today news release.  "In many ways, they are as contaminated or even worse than plants growing on the edges of agricultural fields. That was a surprise, at least to me." 

Forister, who is the Trevor J. McMinn Endowed Professor in Biology, Foundation Professor,  holds a doctorate in ecology from UC Davis, where he studied with major professor Art Shapiro, UC Davis distinguished professor of ecology and evolution. 

Forister's doctoral student, Christopher Halsch, is the lead author of the paper. “The farther along in the life stage you go, the higher concentration you need to have a sublethal effect," Halsch explained. "For the caterpillars, this means a low concentration can have a more damaging effect than it would have on the butterflies.”

So did the plants labeled "wild-life friendly" have fewer pesticides on the leaves? No.

 “That was the most shocking part," Halsch related. "The fact that plants labeled as potentially beneficial or at least friendly to wildlife are not better and in some cases might be worse than other plants available for purchase. This research sheds light on how pesticides may impact western monarchs, but many other butterflies are facing even steeper population declines, and pesticides are likely one driver.”

Thus, it's crucial that those milkweed plants that we purchase in retail stores--and elsewhere--be pollinator friendly and pesticide-free.

AsXerces' Pesticide Program Director Aimée Code, pointed out in the news article: “Everyone can take steps to address the risks we uncovered. Consumers can let their nurseries know they want plants that are free from harmful pesticides. Nursery outlets can talk with their suppliers and encourage safer practices, and government agencies can improve oversight. And it's important to keep gardening for pollinators for the long term, just take steps to reduce pesticide exposure: cover new plants the first year, water heavily, discard the soil before planting, as it may be contaminated, and avoid pesticide use.” 

We asked entomologist and monarch researcher David James of Washington State University today what he thinks of the study: "We all suspected this was the case, given all the reports in social media of caterpillars dying, etc.  I'm glad they did this scientific study to confirm it. Pretty shocking, really."

Indeed, scientists fear that the rapid decline of monarchs could lead to extinction. The International Union for the Conservation of Nature (IUCN) placed the migratory monarch butterfly on its Red List of threatened species on July 21, 2022, classifying it as endangered. 

"In the 1990s, nearly 700 million monarchs made the epic flight each fall from the northern plains of the U.S. and Canada to sites in the oyamel fir forests north of Mexico City, and more than one million monarchs overwintered in forested groves on the California Coast," according to the Xerces Society. "Now, researchers and citizen scientists estimate that only a fraction of the population remains, monarchs have declined by more than 80% since the 1990s from central Mexico, and by more than 99% since the 1980s in coastal California."

The public tends to blame habitat loss and pesticides for the declining butterfly populations in the Western United States.

But climate change, aka global warming, may be an equal, if not more, of a factor.

So indicates a 10-member team of scientists, including UC Davis distinguished professor Art Shapiro, Department of Evolution and Ecology, in the March 4th Science journal. 

The research article, "Fewer Butterflies Seen by Community Scientists Across the Warming and Drying Landscapes of the American West," sounds a crucial alarm, alerting us to try to find new ways of protecting our fluttering friends.

The abstract:

"Uncertainty remains regarding the role of anthropogenic climate change in declining insect populations, partly because our understanding of biotic response to climate is often complicated by habitat loss and degradation among other compounding stressors. We addressed this challenge by integrating expert and community scientist datasets that include decades of monitoring across more than 70 locations spanning the western United States. We found a 1.6% annual reduction in the number of individual butterflies observed over the past four decades, associated in particular with warming during fall months. The pervasive declines that we report advance our understanding of climate change impacts and suggest that a new approach is needed for butterfly conservation in the region, focused on suites of species with shared habitat or host associations."

Lead author is UC Davis alumnus Matthew "Matt" Forister, the Trevor J. McMinn Endowed Professor in Biology, and Foundation Professor, Department of Biology, University of Nevada. Forister received his doctorate in ecology from UC Davis in 2004.

Writer Elizabeth Pennisi, in her article in sciencemag.org, provides this quote from Jessica Ware, an American Museum of Natural History entomologist (she was not involved in the study): “If humans don't take dramatic steps to curb global warming, entire ecosystems could disappear, with untold impacts on biodiversity and human health."

As Pennisi points out, "butterflies are at risk in open spaces, too." She writes: "Art Shapiro, an insect ecologist at the University of California, Davis, and colleagues have shown that over the past 35 years, butterflies are disappearing even in pristine protected areas such as the Sierra Nevada mountain range in the western United States."

"To see whether that finding held up elsewhere, Shapiro and Matthew Forister, an insect ecologist at the University of Nevada, Reno, gathered data from the North American Butterfly Association, which has coordinated community scientist butterfly counts across the United States for more than 42 years. The duo also incorporated 15 years of data from iNaturalist, a web portal that collects sightings of plants and animals, including butterflies. In all, the researchers tracked the fates of 450 butterfly species from 70 locations in the western United States."

The research indicates that the butterfly population in the Western United States has decreased an average of 1.6% per year between 1977 and 2018.  "Fifty species declined in at least two of the data sets used, including the Edith's checkerspot (Euphydryas editha), the rural skipper (Ochlodes agricola), and the great copper (Lycaena xanthoides)," Pennisi wrote.

The researchers warn that some species may completely disappear from parts of their ranges in the coming decades, as fall temperatures continue to align with or exceed summer temperatures, impacting breeding cycles and plant dependence.  

Not Just Monarchs in Trouble
Back in February, 2019, Shapiro told the Environmental Defense Fund's UC Davis meeting on "Recovering the Western Monarch Butterfly Population: Identifying Opportunities for Scaling Monarch Habitat in California's Central Valley," that it's not just monarchs in trouble.

"Monarchs are in trouble in California--but they're hardly alone," Shapiro told the attendees.  "If we act as if this is a 'Monarch problem,' we're in danger of missing the real causes of Monarch decline--factors acting at a much broader scale. We've been monitoring entire butterfly faunas--over 150 species--along a transect across California since 1972. Our monitoring sites are matched with climatological data, allowing us to examine statistical relations between climate and butterfly trends. Based on this data set, our group was the first to document and publish evidence of monarch decline here. That's the only reason I'm here."

"At low elevations—below 1000'—entire butterfly faunas have been in long-term decline. We published several papers showing that these declines were about equally correlated with land-use changes and pesticide (especially neonicotinoid) use, with climate change a significant factor but much less important. Remember, these are correlations, not necessarily demonstrations of causation—but they are strongly suggestive. Monarchs were just one of many species going downhill; three once-common species (the Large Marble, Field Crescent and “Common” Sooty-wing) had already gone regionally extinct or nearly so, with others threatening to follow suit."

See more of Shapiro's comments on the March 4, 2019 Bug Squad blog. Read the Science article here.