Welcome to Art's Butterfly World

This website describes over 34 years of data collected by Dr. Arthur Shapiro, professor of Evolution and Ecology at the University of California, Davis, in his continuing effort to regularly monitor butterfly population trends on a transect across central California. Ranging from the Sacramento River delta, through the Sacramento Valley and Sierra Nevada mountains, to the high desert of the western Great Basin, fixed routes at ten sites have been surveyed at approximately two-week intervals since as early as 1972. The sites represent the great biological, geological, and climatological diversity of central California.

As of the end of 2006, Dr. Shapiro has logged 5476 site-visits and tallied approximately 83,000 individual records of 159 butterfly species and subspecies. This major effort is continuing and represents the world’s largest dataset of intensive site-specific data on butterfly populations collected by one person under a strict protocol. We have also collated monthly climate records for the entire study period from weather stations along the transect.

We built this website as a portal for Dr. Shapiro’s data and observations, supported by National Science Foundation Biological Databases and Informatics Grant DBI-0317483. Much of the data is freely available (Please Contact Us for more information).

Looking Backward -- 2019

Click the link to download: Looking Backward 2019 (.pdf)

Meet the scientist who’s been counting California butterflies for 47 years and has no plans to stop

This article appeared in the Los Angeles Times on Nov. 12, 2019, and was written by Deborah Netburn.

Here's the link: https://www.latimes.com/science/story/2019-11-12/california-butterflies-scientist-art-shapiro

Looking Backward -- 2018

Click the link to download: Looking Backward 2018 (.pdf)

Looking Backward -- 2017

Click the link to download: LOOKING BACKWARD 2017 (.pdf)


Click the link to download: LOOKING BACKWARD 2016 (.pdf)

Looking Backward -- 2015

Click the link to download: LOOKING BACKWARD 2015 (.pdf)

Looking Backward -- 2014

Click the link to download: LOOKING BACKWARD 2014 (.pdf)


Click the link to download: SEPTEMBER SONG (.pdf)

Donner Summit Historical Society Newsletter featuring Butterflies

This issue of the of the Donner Summit Historical Society Newsletter features Art's butterfly study, and focuses on the Donner Pass collection site.

‘Butterfly man’ finds clues to climate change

In a functional classroom in a functional building on the UC Davis campus, Arthur Shapiro sits unassumingly in the corner. Rumpled, wearing well-worn Converse All Star tennis shoes, old jeans and a faded, zippered green hoodie, Shapiro could be just another student, except for his weathered face and bushy gray beard.

In fact, Shapiro happens to be one of the world’s leading butterfly experts, a “biodiversity guru,” as one of the students in the class puts it, or “a walking encyclopedia,” says another—and, as it happens, the mastermind behind one of the United States’ leading indicators of a changing climate as well as a changing landscape.

Read the rest of the story at newsreview.com:

Painted Ladies, To Be or Not To Be?

Update: During the week of April 11, 5 more migrating Painted Ladies have been observed at various locations, all going N. There thus appears to be a migration afoot, but a minimal one!

Update: On March 12, 2011 at 11:54 AM, a Painted Lady in migratory mode, flying rapidly from SE to NW about 6' off the ground, was observed at Suisun City, Solano County--the first record this year known to me. It was small and pale, of the migratory desert phenotype.


I’ve begun receiving inquiries about whether or not to expect a Painted Lady (Vanessa cardui) migration this spring. In good years they would already be showing up, but there have been no reports so far anywhere in California, to my knowledge. The phenomenon depends on breeding success in the desert wintering grounds, which in turn depends on the rains producing a good crop of annuals for the larvae to feed on. After good late autumn and December rains, the tap was turned off for seven weeks—just like here—and the early annuals either dried up or froze. There were good rains over the President’s Day weekend—almost 2 inches at Anza-Borrego—which have already triggered another round of germination. But is it too little, too late? It all depends on March. 1992 had a very wet March after a dry midwinter. However, the northward migration is controlled by photoperiod (we think), and any butterflies that are around in March will head north rather than try to breed down south. So the timing is dicey. As of now, I would NOT expect a big flight here this spring.

Western Tiger Swallowtails

The "outbreak" of Western Tiger Swallowtails has continued for a second year. Elevated populations are reported at least as far east as Reno and as far west as Fairfield and Vallejo. The "epicenter" seems to be in Davis, however, where it has been on the wing every week since the last week of March, with no clear break between generations (very unusual), and at times in certain neighborhoods (e.g., College Park) one could see 5 or 6 individuals at one time. The phenomenon has attracted a lot of interest from the general public, which is unsurprising--and no, we don't have an explanation for it! (Wish we did.)

Butterflies affected by Climate and Development

A new study covering 159 species of butterfly that were monitored for over 35 years has just been published in the Proceedings of the National Academy of Sciences. This is the first major paper resulting from the remarkable research program of Professor Art Shapiro at UC Davis. Art's project consists of 11 sites which he visits every two weeks, and extend from Suisun Marsh in the Bay Area, across the central valley, and up and over the Sierra Nevada to a final point at Sierra Valley on the east side.

Their most significant findings:

  • Butterfly diversity (the number of different species present) is falling fast at all the sites near sea level, in the central valley, and the foothills. It is also declining, but more slowly, in the mountains.
  • The highest monitoring sites, at tree line, show an increase in butterfly diversity, as lower-elevation species react to the warming climate by moving upslope to higher, cooler elevations.
  • However, among butterflies adapted to the highest elevations, the number of species is beginning to fall because temperatures are becoming uncomfortably warm for them.

“There is nowhere to go except heaven,” Shapiro said.

Another surprising finding was that ruderal (“weedy”) butterfly species that breed on “weedy” plants in disturbed habitats and are highly mobile are actually declining faster than “non-weedy” species — those that specialize in one habitat type.

Gulf Fritillary colonizes Sacramento and Davis

Agraulis vanillae

Agraulis vanillae

There’s a new butterfly in town in the Sacramento metropolitan area. Well, almost new: it’s back after about 40 years. The Gulf Fritillary has returned, and it’s even breeding in midtown.

The Gulf Fritillary, whose scientific name is Agraulis vanillae, is one of the showiest butterflies in California. It has long, narrow bright orange-red wings with black spots on the upper surface. But it’s the underside that shines: it’s spangled in iridescent silver. Nothing else in the region looks like it. Its wingspan can reach four inches.

This is a tropical and subtropical butterfly, whose range extends from the southern United States all the way to central Argentina. Its spiny orange-and-black caterpillar feeds only on Passionflower leaves, eating many but not all species of the genus Passiflora. There are no native members of this genus in the state of California, but several are widely cultivated in gardens. The butterfly can only breed where there is a "critical mass" of these plants in a town or neighborhood, according to Arthur Shapiro, professor and butterfly expert at the University of California, Davis.

About this Study

Art Shapiro at Gates Canyon

Art Shapiro at Gates Canyon

Phenology has interested me for going on half a century. I began keeping phenological records of butterflies as a teenager in Philadelphia. As an undergraduate at the University of Pennsylvania I took a community ecology course from Jack McCormick, who was under contract to do an ecological study of the Tinicum wetlands (near Philadelphia International Airport). I had been doing an informal faunistic study of the place, purely for the fun of it, and had tons of data. A summary of this work was ultimately incorporated into Jack’s report. The study had a significant phenological component. Harry K. Clench, a butterfly taxonomist at the Carnegie Museum in Pittsburgh and one of the founding members of the Lepidopterists’ Society, published a phenological study of the butterflies of the Powdermill Nature Reserve in southwestern Pennsylvania, and sent me a copy. As I recall, we had already corresponded about the occurrence of unusual Hairstreaks (Lycaenidae) in southeastern Pennsylvania, a subject on which I had published field notes at a tender age. Thus began a correspondence on phenology which continued until Harry’s sudden death. Harry was “into” curve fitting. He had a sine function that worked pretty well for Powdermill, but not for Philadelphia. I was very leery of the approach: prediction was useful, but not nearly so useful as a method that cast light on the underlying mechanisms. The parameters in Harry’s equations were not obviously biologically meaningful.

Book: Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions

Authors:  Arthur M. Shapiro and Tim Manolis
Publisher:  University of California Press

The California Tortoiseshell, West Coast Lady, Red Admiral, and Golden Oak Hairstreak are just a few of the many butterfly species found in the floristically rich San Francisco Bay and Sacramento Valley regions. This guide, written for both beginning and experienced butterfly watchers by one of the nation's best-known professional lepidopterists, provides thorough, up-to-date information on all of the butterfly species found in this diverse and accessible region. Written in lively prose, it discusses the natural history and conservation status for these butterflies and at the same time provides an integrated view of butterfly biology based on studies conducted in northern California and around the world. Compact enough for use in the field, the guide also includes tips on butterfly watching, photography, gardening, and more.

  • Discusses and identifies more than 130 species
  • Species accounts include information on identifying butterflies through behavior, markings, and host plants
  • Beautiful full-color plates illustrate top and bottom views of wings for easier identification
  • Includes a species checklist and a glossary

Buy this book online
To purchase the book or see more details from the UC Press website, visit the following link. UC Press Bookpage

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