Last summer, some friends were visiting my butterfly garden. A third-grader was with them and he had many questions. The big question came when I said that butterflies go through metamorphosis.
His ears perked up and he wanted to know what that was. I explained the process to him with many anise swallowtail and pipevine swallowtail pupae in front of us.
Most insects, bees, bugs, spiders, lady bugs, moths and butterflies go through complete metamorphosis. They need different foods at different stages of this cycle, and these foods are not available year around. Butterflies, native bees and other insects developed over millennia along with the plants they depend on to survive.
Napa County has many native bee species, and 30 percent of them nest in wood. They seek holes and cracks in wood to build their nests. When I drilled holes in a big piece of firewood, mason bees immediately took it over. Inside the holes, they prepare nests for their eggs with some nectar or small dead bugs. They put a bit of mud between the cells and build as many cells as will fit in the holes. Then they seal it with mud.
The eggs hatch into larvae (caterpillars), the next stage of metamorphosis. The larvae feed on the food the mother bee left for them and form pupae. When the fruit trees start blooming in spring, the pupae hatch and the new bees emerge from the wood and start the process all over again. In my garden, the mason bees rebuilt their empty nests quickly.
Bumblebees have different habits; they nest in the ground. The queen overwinters and is always the largest bee in the hive.
The bumblebees’ cousins, carpenter bees, build their nests in wood that they can easily drill out. They can be very destructive of unpainted wood and sometimes leave a big pile of sawdust.
Butterflies display many different methods of metamorphosis. Pipevine swallowtails start emerging in March and April when the pipevine (Aristolochia californica) begins to bloom and leaf out. That vine is the host plant, the only one that the larvae will eat.
I spend five weeks raising the caterpillars from the day the eggs hatch until they go into pupae. Some of the pupae will remain that way until the following spring, but about half of them emerge over the summer. The pipevine plant seems to last all summer in many places, and the butterflies can lay their eggs and go on their way.
The anise swallowtail has also changed its life-cycle timing because fennel (Foeniculum vulgare), its host plant, has naturalized and is available most of the summer.
The most famous butterfly — everyone’s favorite — is the monarch, which overwinters as a butterfly. Unlike eastern monarchs, ours remain on the coast from Monterey to Southern California. They do not breed in winter. When spring arrives, they start moving north. Along the way, they feed on nectar-rich flowers and lay eggs on young milkweed (Asclepias sp.).
The monarch’s cycle is faster than the swallowtails’. A swallowtail egg takes five to seven days to hatch into a caterpillar; monarch eggs hatch in four days. When the larva leaves the egg, the first thing it does is eat its eggshell and then start eating its larval foods. Monarch larvae increase in size many times in two weeks, from 1/4 inch to 2-1/2 inches. During this time, they shed their skin four times to give them room to grow.
They are also eating like crazy. When they shed their final skin and become pupae, they start to go into metamorphosis.
During metamorphosis, all of the parts of the caterpillar reassemble themselves inside the pupa (also called the chrysalis) into the future butterfly. At the end of 14 to 16 days, a new shiny butterfly emerges. It rests for a few hours, pumping its wings, and then the cycle begins again.
If you would like to know more about the bugs, bees and butterflies around us, I recommend “California Bees and Blooms and Peterson Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley.”
Workshop: U. C. Master Gardeners of Napa County will host a workshop on “Creating Holiday Wreaths” on Sunday, Dec. 11, from noon to 3 p.m., at the Yountville Community Center, 6516 Washington St., Yountville. Learn what plants in your garden could make good wreaths for decorating. Learn how to choose and prepare plant materials so they will look good for a long time. Learn tips and tricks for designing and making easy wreaths for the holidays or any time. Participants will create their own wreath to take home, made from locally collected plant materials. The cost is $20 for Yountville residents; $23 for non-residents. Register with Yountville Parks & Recreation or call 707-944-8712.