The Brutal Life of Butterflies
By Jon Aull
Oh, to live the life of a butterfly drifting gracefully from flower to flower, sipping sweet nectar. Butterflies can be enjoyed for their beauty as “floating flowers,” but they also have fascinating life histories. Behind this seemingly idyllic pastoral life, like any animal, they are locked in a battle for survival.
Since caterpillars don’t get around much, butterflies need to lay their eggs on a plant that is suitable for feeding, called a “host plant.” Some caterpillars feed on a variety or a family of plants. Some, however, have a specific host plant and their caterpillars will eat nothing else. The Pipevine Swallowtail, our most common butterfly in Bidwell Park, uses only the Pipevine as a larval host. Without that plant, we wouldn’t have that butterfly. The California Dogface, our state insect, has largely disappeared from our area due to the disappearance of its larval host plant, False Indigo, as a result of development.
Not only does the Pipevine Swallowtail get nourishment from the pipevine, it also gets protection. The pipevine has toxins in it that the caterpillar sequesters to protect itself from predators. This black caterpillar has orange cone-shaped protuberances that serve as a warning to hungry birds, much as orange cones on a road advertise road hazards. This is particularly helpful when the larvae start their short migration from host plant to pupation site, when they can be a common sight on roads and trails in the Park. The adults also contain the toxins, as do their bright orange eggs.
Another common butterfly in the Park, the Buckeye, has a different strategy for dealing with predators.
Often seen sunning itself on the ground, the Buckeye has prominent eyespots on the wings that distract birds from the nutritious body and let the butterfly get away with its life. As many as 10% of Buckeyes in a population may have wing damage from birds, so apparently it works. Yes, butterflies can fly with pieces of their wings missing, as well as with missing scales, although it can throw them off balance. The scales come off for easy escape from spider webs. While butterflies can survive with wing damage, I imagine it’s like a person living without an arm. You can live, but it makes it a lot easier with all your pieces intact. Eyespots are not just for adult butterflies. The larva of the locally common Tiger Swallowtail has inflatable eyespots that make the caterpillar look more like a snake head.
Another trick some butterflies use is mimicry, which is where a relatively harmless and tasty bug looks like a poisonous one. One local example is Lorquin’s Admiral (named after a failed forty-niner, and California’s first butterfly collector). It has orange spots similar to the distasteful (to birds) California Sister, although, in studies, birds ate the Admiral. Perhaps the sister is distasteful for its habit of feeding on dung and roadkill.
Some butterflies enlist the aid of defenders to help them through life. Larvae from the blue family enlist the help of ants, feeding the ants with a honeydew secretion. The Acmon Blue is a common local butterfly with a range throughout California. Some caterpillars of this family are even taken into the ant nest, where they eat ant larvae and are tended by the ants through the pupal stage, emerging from the ant nest as adults. Some members in this family even communicate with the ants by “stridulating,” or making rasping sounds that mimic hungry ant larvae.
As if predators aren’t enough, winter can be hard on a small cold-blooded animal. There are different strategies for dealing with the weather.
The Buckeye usually overwinters as an adult in the more sheltered foothill canyons. This proved to be a dangerous strategy in the cold snap of Christmas week 1990, when most of them were wiped out. They have since repopulated the area. Some, like the Variable Checkerspot, overwinter as dormant caterpillars, an arrest of development called “diapause.” The Silvery Blue spends nine months of the year as a pupa. Some butterflies overwinter as eggs. Another way to avoid the cold is to migrate. The monarchs are the most famous of the migrators. Ours spend the winter on the central coast, while those from the rest of the country go to Mexico. Our Painted Ladies overwinter in the desert on the US-Mexico border. It’s interesting to note that the long range migrating butterflies breed in their wintering range (and sometimes along the migration route), so the butterflies that are “returning” are not the same that left. How they know where to go is a mystery. Wet years in the desert cause population surges in the Painted Ladies, and it was estimated that over a billion of them migrated through the Sacramento Valley in 2005.
So whether it’s trying to find a suitable place to lay its eggs, avoid predators, or avoid the extremes of temperature, the life of a butterfly can be brutal, and learning more about their lives gives one respect for these seemingly carefree “floating flowers.”
"The caterpillar does all the work but the butterfly gets all the publicity." --Attributed to George Carlin
For more info on butterflies, check out the excellent and definitive book by Arthur Shapiro and Tim Manolis: Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions.
See some of the butterflies from this article and more at the exhibit Butterflies by John Hendrickson, ongoing at the Chico Creek Nature Center.