Invite a Caterpillar to Lunch—As Baby Food for Your Avian Friends
Written by Linda Shepherd
Master Gardener, Sammamish Steward, and member of Washington Native Plant Society
I never thought I’d smile when I saw bug-damaged plants. I’d always loved smoke trees because no bugs eat them. Their purplish-red leaves are always so beautifully intact. That is often true of cool-looking “exotic” plants bought at nurseries since they are usually species imported from other parts of the world. The horticultural trade advertises “pest-resistant plants” and plants that “repel unwanted insects.” And who wants to buy lunch for bugs?
As a Master Gardener, I learned to identify pests and diseases, as well as to have tolerance for a certain amount of plant damage. But people who come to our Master Gardeners clinics with tattered plants usually want to know how to discourage or kill “pests” that eat their plants. Pest control includes spraying caterpillars with pesticides. But even organic pesticides such as neem oil are non-specific and end up killing beneficial insects as well as pests. At clinics, no one has ever asked me what to plant to feed caterpillars.
It wasn’t until I read Doug Tallamy’s Nature’s Best Hope: A New Approach to Conservation That Starts in Your Yard that I made the connection that birds need caterpillars to raise their young. While many birds eat berries produced by native and ornamental plants in the fall, they also need soft, high protein food for their nestlings in spring. For them, caterpillars are the perfect baby food. I was amazed to learn it takes 6000–9000 caterpillars to raise a chickadee family! It still boggles my mind. And caterpillars need to feed on plants before they transform into the pretty butterflies and moths that lighten our spirits with their fanciful beauty and pollinate our flowers.
While adult butterflies and moths can drink nectar from many nonnative flowers, which have less in the way of toxic phytochemicals than leaves, most larvae don’t eat nonnatives. Only about 10% of insect species are generalists that can feed on nonnative plants.
Plants have phytochemicals, such as pyrethrin in chrysanthemums and nicotine in tobacco, that deter herbivores. Over the millennia, herbivores like insects have evolved the ability to tolerate or detoxify specific phytochemicals in a particular group of plants. Just as milkweeds are the required host plants for the monarch butterfly, so other specialist species have evolved to eat specific native plants.
With all the loss of wild lands due to agriculture and development, we have lost many species of pollinators and birds, and populations of remaining species are declining. Homeowners can help offset the loss of habitat by planting native plants to feed caterpillars—who in turn feed birds.
To do my part, I’ve been removing ivy and periwinkle from my yard this summer so I can plant those areas with salal (Gaultheria shallon), pearly everlasting (Anaphalis margaritacea), Western bleeding heart (Dicentra formosa), and oceanspray (Holodiscus discolor). For more plants that caterpillars eat, see Some Washington Caterpillars, the full Douglasia article “How to Support Your Local Caterpillars” (fall/winter 2020, p. 21) by Regina Johnson, and Real Gardens Grow Natives: Design, Plant, and Enjoy a Healthy Northwest Garden by Eileen Stark.
Now, when I see caterpillars eating my plants, I view them in the context of a larger process of Life, an integral part of the cycles of Nature. I smile rather than grit my teeth. I shoot photos of the caterpillars rather than shoot them with pesticide.
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Sidebar: Where to Buy Native Plants on the Eastside
Wildflowers Northwest — native plant nursery in Maple Valley
Tadpole Haven Native Plants in Woodinville
Watch for plant sales by WNPS
Caterpillars can be challenging to identify, but one species of green inchworm develops into the lovely Blackberry Looper Moth, Chlorochiamys chloroleucaria
Photo of a yummy, high-protein treat for nestlings — a Geometer moth caterpillar a.k.a. inchworm or looper (Geometridae family) feeding on the leaf of the native Western Canada Goldenrod (Solidago lepida). Photo credit: Mary Johnson
The Police Car Moth larva (Gnophala vermiculata) is a foodplant specialist that feeds on mountain bluebells a.k.a. lungwort (Mertensia spp.) and a number of other plants in the Borage family (Boraginaceae).
Photo credit: MJ Raupp
Reference Photo credit: Jan Bird
Adults feed during the day on nectar of herbaceous flowers such as thistle (Cirsium spp.) and goldenrod (Solidago spp.). Photo credit for adult