California Tortoiseshell

Raising California tortoiseshells can be a wonderful project if the butterfly is generally common in your mountain canyons in the early spring as well as the late summer or early fall. In between those timeframes, during the months of April, May, June, and sometimes, July, depending upon location and elevation, caterpillars of this butterfly can be found in clusters on several species of Ceanothus including Ceanothus velutinus (mountain lilac).

The two hurdles to raising this butterfly is 1) not being able to recognize its host plant; which this presentation will help you do and 2) looking for caterpillars during years where numbers of this butterfly are limited.

It is true that population numbers of California tortoiseshells can fluctuate greatly in the Western U.S. Again, before seeking caterpillars, keep close watch on how common this butterfly is in the early spring and fall.

California Tortoiseshell Adult Series

Here is a photo of two males and two female California tortoiseshell butterflies. The males are on the left and the underside (ventral surfaces) are below.
Snow Brush Host Plant

Close up shot of one of the larval host plants of the California tortoiseshell, snowbrush (Ceanothus velutinus) growing in a canyon near Leavenworth, Washington. When looking for caterpillars, either seek small clusters of black spiny larvae or look for larger larvae. This host also feeds larvae of the pale swallowtail, hedgerow hairstreak, spring azure, brown elfin, and other butterflies.
Snow Brush in bloom
Late Instar Caterpillar on Snowbrush

If there are many California tortoiseshell caterpillars on snowbrush, it is usually not too difficult to locate them as they are mostly black with spines against green leaves and/or white blossoms in the background. Always remember that females lay eggs in large clutches. Scan the bush for larvae; but don't spend too much time looking. If you find one larva, you may very well find many; but if don't find any (which is more often the case) move on to another bush.
California Tortoiseshell Caterpillars in Five Gal. Bucket

Place cuttings of snow brush in bottled water. Cork the opening with toilet or facial tissue; so that the plant goes through to the water; but caterpillars cant'. Replace host every five days or so or when caterpillars have depleted cuttings. Make sure your lid either has holes or cut a hole out of the lid and place screen over the hole so that caterpillar frass will dry and not get your larva sick.
Five Gallon Rearing Bucket with Lid

Note that the lid on the bucket has a large hole with netting material fastened to the lid so that caterpillars cannot escape. The sheet of glass you see in this photo is not needed for raising California tortoiseshells.
California Tortoiseshell Fifth Instar Caterpillar
California Tortoiseshell Fifth Instar Caterpillar

Series of photos I took of a fifth instar caterpillar from Skyline Drive heading towards Bountiful Peak, Davis County, Utah.
California Tortoiseshell Fifth Instar Caterpillar
California Tortoiseshell Fifth Instar Caterpillar

Photo taken outside.
Young Fifth Instar Caterpillar
California Tortoiseshell Pupa Emerges

Photo collage of developing pupae and recently emerged adult female. Photos courtesy Nicky Davis.