Help for the Insect Apocalypse: Calscape Adds Host Plant Information for California Native Butterflies and Moths

Contact: Liv O’Keeffe
916-447-2677, ext. 202

An El Segundo blue butterfly with its host plant, sea cliff buckwheat (Eriogonum parvifolium) Photo: Ann Dalkey

June 19, 2019, SacramentoThe California Native Plant Society announced today that its Calscape native plant database now includes host plant information for California native butterflies and moths (Lepidoptera). For these insects, host plants are those on which they can lay their eggs and their caterpillars can eat — and only specific plants will do.

Now, people can go to and type in any California address to see which butterfly and moth species are native to their location, and which native plants to grow for those moths and butterflies. Calscape users also can select from more than 1,300 butterfly and moth species to see which plants those species need to survive.  For example, Pasadena users can quickly see the 240 native butterfly and moth species native to their location and view the list of host plants on which they depend. They can also view the host plants to support any selected species, such as Monarch and Lorquin’s Admiral at their location.  

“If you care about the collapse of butterflies and other pollinators, this is a simple tool you can use to help in a very real way,” said ecologist Douglas Tallamy, one of the nation’s most published researchers on the specialized relationships between native plants and insects. Research shows 90 percent of butterfly and moth species can only eat the native plant species with which they’ve co-evolved. If a given species of butterfly or moth can’t find its particular host plants in the area it resides, it will die out in that location.  “The problem is loss of habitat, so restoring these host plants to our neighborhoods and green spaces is a powerful solution.”

Caterpillars and insects need native plants to survive, and creatures further up the food chain need those insects, especially caterpillars. For example, Tallamy’s popular book, Bringing Nature Home, explains that 96 percent of terrestrial bird species rely on insects to feed their young, and fat juicy caterpillars are a key part of that diet.  So if the required native plants are not present in an area, most of the butterfly and moth species will die out in that area along with much of the other animal life that depends on them.

“We hope this new tool will lead to many more people growing the native plants that support our natural ecosystems.,” Calscape creator and project lead Dennis Mudd said. “If enough people join in, we can help mitigate the loss of biodiversity we’re now seeing in California.”

Acting locally

Retired marine biologist and CNPS Garden Ambassador Ann Dalkey took it upon herself to address habitat decline in her community with the help of her local CNPS South Coast Chapter.

More and more people are recognizing that the place to expand habitat is within our urban landscapes,” she said.

Together, Dalkey and the CNPS South Coast Chapter started the Patch Habitat Program to expand habitat for their local El Segundo blue butterfly and other local native butterfly species. To do so, they planted sea-cliff buckwheat (Eriogonum parvifolium) and additional host plants in residential and urban landscapes. As part of the effort, volunteers planted hundreds of sea-cliff buckwheat in the chapter’s Point Vicente Interpretive Garden in Rancho Palos Verdes, where visitors can learn about the butterfly and the importance of habitat. Today, just about every plant in the garden supports some kind of butterfly, said Garden Manager Megan Wolff.  

“It’s about finding the sweet spot between landscaping and creating habitat,” said Cris Sarabia, a CNPS board member, co-founder of Flora y Tierra in Long Beach, and active member of the South Coast Chapter.

About the new data

The Calscape team created the new tool by integrating:  

  • Geographic range maps of the plant species native to California based on more than 2 million field occurrences provided through the Jepson Herbarium at UC Berkeley and the participants of the Consortium of California Herbaria.
  • Thousands of butterfly and moth images with the help of CalPhotos.

“We want to acknowledge every organization, intern and field researcher who conducted the painstaking business of properly recording and digitizing these kinds of records,” added CNPS Executive Director Dan Gluesenkamp. “So, support your nearby research institutions and scientists. This work is never-ending and is needed now more than ever to fight both local and global extinction.”

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About the California Native Plant Society:

The California Native Plant Society is a statewide organization working to save and celebrate California’s native plants and places via plant science, advocacy, education, and horticulture. CNPS has nearly 10,000 members in 35 chapters throughout California and Baja to promote its mission at the local level.


Research on specialized relationships between insects and native plants:

Futuyma, D.J. and F. Gould.  1979.  Associations of plants and insects in a deciduous forest.  Ecological Monographs 49: 33-50.

Bernays, E.M. and M. Graham.  1988.  On the evolution of host specificity in phytophagous arthropods.  Ecology 69: 886-892.

Forister, M. L., Novotny, V., Panorska, A. K., Baje, L., Basset, Y., Butterill, P. T., Cizek, L., Coley, P. D., Dem, F., Diniz, I. R., Drozd, P., Fox, M., Glassmire, A., Hazen, R., Hrcek, J., Jahner, J. P., Kama, O., Kozubowski, T. J., Kursar, T. A., Lewis, O. T., Lill, J., Marquis, R. J., Miller, S. E., Morais, H. C., Murakami, M., Nickel, H., Pardikes, N., Ricklefs, R. E., Singer, M. S., Smilanich, A. M., Stireman, J. O., Villamarín-Cortez, S., Vodka, S., Volf, M., Wagner, D. L., Walla, T., Weiblen, G. D., and L. A. Dyer. 2015. Global distribution of diet breadth in insect herbivores.  Proceedings of the National Academy of Sciences 112:442-447.

Tallamy, D. W. and K. J. Shropshire. 2009. Ranking Lepidopteran use of native versus introduced plants. Cons. Biol. 23: 941-947.

Richard, M., D.W. Tallamy and A. Mitchell. 2018. Introduced plants reduce species interactions. Biological Invasions. DOI:10.1007/s10530-018-1876-z)


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