Today’s selection — from The Life Cycles of Butterflies by Judy Burris & Wayne Richards. Summer butterflies live only for a week or two:
“A butterfly emerges from its chrysalis as a fully grown adult. You may see different sizes of the same species of butterfly, but often the difference is due to factors such as weather and food supply that affected the growing caterpillar. Sometimes the males and females of a species are naturally different sizes; usually the egg-carrying female is larger.
“Most summertime butterflies have a very short life span: about a week or two. During that time the butterflies focus mainly on searching for food and finding a mate. They rely heavily on their keen senses of sight, smell, and taste to locate all the things they need to survive and reproduce.
“Butterflies have large eyes that can see many colors, including those in the ultraviolet range that humans can’t see. If we use special lighting, we’re able to observe that many flowers almost glow with ultraviolet patterns. To the butterflies, these flowers must look like brightly lit runways! Butterflies can also detect movement better than we can — that’s why it can be so difficult to sneak up on them. If a male butterfly sees something fly by that looks like a possible mate, he’ll move quickly to investigate. If it turns out to be a rival suitor, he may chase him out of the area to prevent any competition. If it’s a female, he’ll pursue her, performing his best aerial acrobatics.
“With the chemical receptors on their antennae, butterflies can detect odors in the air. They can locate food, potential mates, and perhaps other things that we don’t even know about. When a butterfly lands on a flower, a mushy fruit, or a patch of tree sap, it can taste the food with its tongue and its feet. The length of a butterfly’s tongue varies by species. Some are capable of feeding from long tubular flowers; those with a shorter tongue must sip from flatter-faced blooms.
“You’re not likely to see many active butterflies when the temperature is below 50°F/10°C. Like all other insects, butterflies are cold-blooded and must bask in the sun on cool days to warm up their flight muscles before they are able to fly. We often see butterflies sunbathing on our stepping-stones.
“The thousands of dusty scales that cover a butterfly’s wings and body absorb heat from the sun. The butterfly can make its wings tremble and shiver to help speed up the warming process. It knows exactly how to orient its wings to the sun so it can absorb heat more quickly. This is important, as a sitting butterfly is vulnerable to attack.
“Some butterflies seem to need more heat than others do. We have observed Mourning Cloak and Question Mark butterflies flying around on very chilly mornings, hours before other species even attempt to fly.
“The scales covering the wings and body also give a butterfly its pretty colors. Some scales are colored by pigments; others are iridescent, appearing shiny or metallic because of the way light hits them. A few are transparent. The scales are loosely attached to the wings and overlap each other, rubbing off easily when touched. This prevents things from sticking to the wings and may make the wings more difficult for a predator to grasp.
“Wing scale colors allow butterflies to recognize each other. Many scales reflect ultraviolet light and act as markers, so species look different from one another. Males and females of the same species also look different from each other. Our eyes can only see these subtle patterns if we view a butterfly under special lighting.
“Most summertime butterflies live only a week or two. Within that short time they urgently seek out a mate so they can reproduce. Because they also need to find food, take shelter from bad weather, and avoid hungry predators, locating a mate can be a daunting challenge.
“Each species of butterfly produces its own pheromones (chemicals that stimulate mating behavior). Potential mates can smell pheromones from a distance, which is a more reliable way of each other than just depending on a chance meeting.
“Once a male and female have sighted each other, some species begin elaborate courtship ‘dances’ involving a lot of chasing and aerial stunts. The male shows off his ultraviolet-reflective wings and the female decides if he’s worthy of her attention. On a few occasions we’ve seen a butterfly get his signals crossed and attempt to mate with a female of a different species. This usually results in the male getting a quick wing slap from the female. Sometimes butterflies will fight if more than one male approaches the same female.
“Some male butterflies are so eager to mate that they seek newly emerged females that are still drying their wings. Since the female can’t fly yet, the male’s success is guaranteed. This strategy saves the male the trouble of impressing a female with his fancy flying by chasing after her, and it allows him to spend his extra time and energy looking for another available mate.”