Have you ever wondered why some butterflies have iridescent blue-black wings and a taste that’s repulsive to birds and other predators? Ron Rutowski, a Tempe resident and biology professor at Arizona State University since 1976, has too — actually, he’s spent years and traveled extensively throughout North and Central America and Australia, studying the ways color is produced, employed and perceived in the animal kingdom, particularly on ways insects use color as a visual signal and how it’s interpreted by their compound eyes.
Rutowski, who moonlights as an Arizona State Parks volunteer, answer some common butterfly questions below, but you can learn much more at the Butterfly Walk he’s leading at 8:30 a.m. Saturday, June 28, at Boyce Thompson Arboretum.
Q. What months are best to see butterflies in Arizona?
A: Arizona gets two pulses of rain each year, the winter rains from November to March and the summer monsoon rains in August and September. Because butterflies are so dependent on plants — the adults for nectar to sip and the caterpillars for leaves to munch — and because our most luxuriant plant growth follows the rains, the spring and fall, and not the summer are good times for looking for butterflies. That being said, there will certainly still be butterflies to be seen in June, just not quite as many individuals and not quite as many different kinds as in the spring and fall.
Q. You share interesting anecdotes about Pipevine Swallowtails. Why do these occur at Boyce Thompson Arboretum? What’s unusual about them?
A. Dutchman’s pipe, the plant eaten by Pipevine Swallowtail caterpillars, is common at BTA and in the surrounding desert; what’s unusual is the iridescent blue color of adult butterflies. For many years, a focus in my lab has been on iridescent colors. These colors by definition are directional, which means they change rather dramatically in appearance depending on the positions of the iridescent animal and the animal looking at it. Biologists have thought for years that this must present special challenges for the animal to make its iridescent color apparent to an intended receiver. So, how do they deal with this directionality? The Pipevine Swallowtail is a great subject for studying this question because they have iridescent blue patches on both their upper and lower wing surfaces. The blue on the upper wings surface is found only in males and is a sexual signal. So, how do males present this signal to females in courtship? The lower wing surface blue is part of their warning coloration that predators learn to associate with the fact that these animals are very unpalatable. So, how does the directionality affect the ability to predators to learn this association? Our answers to these questions should be helpful in understanding the behavior of other organisms with iridescent coloration and animal communication systems generally.
Q. Did you pin colorful butterflies into boxes when you were a kid?
A: No. I was interested and committed to biology by my early teens and at that time my focus was on birds. Bird-watching was an activity my father and I started doing together. My first real interaction with butterflies was as a high school senior in an advanced biology class that made regular trips to a nearby canyon in near Los Angeles and kept lists of animals and plants seen there over the course of a year. After high school, my interest in birds persisted but became more focused on animal behavior and communication. When I got to graduate school I became quickly convinced by my Ph.D. adviser, Dr. Thomas Eisner, of the many interesting and unanswered questions about communication in insects, especially visual communication in butterflies. That was the beginning of a focus on butterflies and the production and function of visual signals that has persisted throughout my career.
If you go
What: Butterfly Walk
When: 8:30 a.m. Saturday, June 28.
Where: Boyce Thompson Arboretum, 37615 E. US Highway 60, Superior
Cost: $10; includes admission to the garden
Information: (520) 689-2723 or Cals.arizona.edu/bta/