N
ot just a children’s book, “The Very Hungry Caterpillar” is a biological truth. A caterpillar is very hungry because it does all the eating for its future life. Remember, adult butterflies have no mouth and can’t eat; they rely on the food stored in the caterpillar’s body to metamorphosize and reproduce. True, butterflies do have a tongue to sip nectar, but that’s not enough nutrition for mating and egg laying. This system cleverly avoids competition for food between the nectar-drinking adults and the leafeating caterpillars. Why Such Specialized Diets? What is the advantage of restricting a caterpillar’s diet to a particular family, genus or species of plant? Since many of the host plants contain toxic chemicals, a complex evolutionary process was required for the caterpillar to first tolerate, then metabolize and finally store the poisons in its body. To repeat this evolutionary process for many kinds of plants would be an inefficient redundancy. Obviously, the disadvantage of this specialization is that if a particular food plant is eradicated, butterflies cannot evolve fast enough to change their diet and survive as a species.
The beloved Monarch is in process of this fate in the United States where a unique subpopulation migrates but can no longer rely on a bountiful supply of Milkweeds in its breeding grounds. Ninety percent of the midwestern Milkweeds has been wiped out by agricultural practices. Simultaneously, the population of Monarchs has declined 90 percent in the past 20 years. This is not a coincidence. How Does a Butterfly Find its Host Plant? Butterflies co-evolved with specific host plants to use their molecules to trigger egg-laying and caterpillar feeding. If those molecules are absent, the gravid female will not her lay her eggs. Locating a host plant is not random. Both males and females use the olfactory receptors in their antennae to smell the host plant’s magic molecules in the air. They then follow the scent trail back to the source. When the female locates a host plant, she lands and confirms the plant’s identity with the taste receptors on her feet. When these taste receptors lock onto the plant molecule, the butterfly will lay her eggs, usually one by one. What happens if she can’t find her host plant? She will die with a
An ample supply of Tropical Milkweed, a favorite Monarch host, will be available for purchase.
LENORA LARSON Butterfly Maven 14
April 2022 | kcgmag.com
Photos by Lenora Larson.
You Are What You Eat
A common garden herb, Rue grows in full sun. It hosts the Black and the Giant Swallowtail. belly-full of unlaid eggs. And the next generation is forever lost. Where Can You Find Host Plants? It used to be almost impossible to find host plants unless the plant serendipitously had human uses like edible Carrots or medicinal Rue. Today, many native plant nurseries and nature-focused plant
If you have a shady spot, buy a native Spicebush, which hosts the arguably cutest caterpillar of all, the Spicebush Swallowtail.
sales carry host plants. The Marais des Cygnes Extension Master Gardener Plant Sale in Paola, Kansas specializes in butterfly host plants plus provides handouts and has volunteers to answer questions. The sale runs from Thursday, April 27 through Saturday, April 29. Please see the ad, article or calendar listing in this issue of The Kansas City Gardener for more information.
Want a new host plant for your Black Swallowtails? Buy Moon Carrot, a gorgeous native of Turkey.
A Marais des Cygnes Master Gardener, Lenora is a member of the Idalia Butterfly Society and Kansas Native Plant Society. She gardens in the clay soil and cruel winds of Paola, KS. She may be contacted at lenora.longlips@gmail.com.
