Biology Bytes: Raising Butterflies

May 24th, 2014

butterfly_hand

Butterflies are the real-life phoenixes in our backyards. Like magic, a bumbling glutinous grub transforms into a majestic winged beauty in a process that seems like a second birth. Are butterflies consciously reborn the moment they emerge from their pupal prisons? Or is their consciousness a continuation of what they experienced as caterpillars? What accounts for the dramatic metamorphosis?

Probing the inner workings of a pupa is hard to do without disrupting the delicate transformation process, so scientists have traditionally had a difficult time investigating what really happens inside the cocoon or chrysalis. Fortunately they now have indirect means of gathering data about what’s happening during a butterfly metamorphosis, and it’s more interesting than I originally imagined.

Although I don’t have the tools to make cutting-edge discoveries about butterflies myself, simply watching these creatures develop on their own and researching about them online has taught me quite a lot. Butterflies are inspiring pieces of living logic! An incredible amount of design is packed into these magnificent little creatures. Watching them grow up is an unforgettable experience.

What follows is a brief account of what I observed and learned from doing research online about my painted lady butterflies.

Larva Stage

I ordered five live caterpillars along with their food and expandable butterfly habitat. Within days after arrival, the caterpillars grew at least three times their original size. They glutinously feasted on the nutrient-rich formula that came with the kit. Fortunately, I didn’t have to do much other than keep them out of direct sunlight. Painted lady caterpillars make very low-maintenance pets! They seem to be perpetual eating machines, however. They quickly grow from scrawny worms to plump sausages in a matter of days.

caterpillar_still1

As the caterpillars grew, they shed their exoskeletons, leaving black crumpled balls all over the place. They also created towering mounds of waste and silken webs around the edges of the container.

Pupa Stage

Eventually a caterpillar shed its exoskeleton for the last time. It finds a place to hang upside down and attaches itself with silk so that it can effortlessly dangle by its hind feet. For the next few hours, it appears to be doing sit-ups in slow motion. What it’s really doing is shedding its skin for the last time. It pushes itself out of its own skin head first. The body that emerges is a smooth, hard casing called the chrysalis.

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Note: A chrysalis is not the same thing as a cocoon. Some larvae (e.g. silk worms) produce casings out of soft, silky bags called cocoons. Painted ladies, by contrast, transform from a caterpillar to a butterfly inside a hard protein shell.

Defense Mechanism: Insects evolve many ingenious ways to protect themselves from predators. The vulnerable pupa is no exception. Rather than just hang around passively, a pupa will usually shake violently in response to a perceived threat. One time, I was fortunate enough to catch it on film! Other species of pupa are known to even make squeaking sounds if disturbed (2).

Contrary to popular belief, a caterpillar does not completely dissolve into an amorphous soup inside the pupa. While it’s true that a caterpillar partially digests itself, many of the caterpillar’s original structures don’t change much (2). Some research suggests that butterflies even retain memories from the larval stage, suggesting that the brain stays in tact during metamorphosis (3). A butterfly’s adult structures start off as imaginal discs, hidden structures within the caterpillar that reflect its adult characteristics. These imaginal discs gain cells to become fully defined adult features (e.g. wings, antennae, proboscis). The left over materials that were used to augment these imaginal discs are later discarded as a fruit-punch-colored waste product called meconium.

pupa_still

As the metamorphosis nears completion, the orange wings become visible through the chrysalis. The chrysalises reminded me of beautiful gems with their iridescent shine and symmetry.

Adult Stage

When the butterflies hatched from their chrysalises, I didn’t have time to catch any of it on film. It all happened so fast! At first, the chrysalis broke open along the seams. The butterfly pushed the flap open with its forelegs and immediately wriggled out. Its wings started off shriveled and wet, but over the course of an hour, it pumped blood into its wings until they were full size. As the wings expanded, the abdomen shrank. I also noticed that the butterfly appeared to be bleeding. Fortunately, that clear red liquid was just harmless excretion leftover from the pupal stage.

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Food: Adult butterflies don’t eat solid food. Instead, they drink the sugary nectar of flowers through a straw-like appendage called a proboscis. (It looks a bit like one of those roll-up party favors that people blow on to produce annoying sounds). During the time I kept the adult butterflies in captivity, I fed them orange slices and watermelon chunks.

After keeping the adult butterflies for about a week, I let them go in a horse pasture near my house. Watching them fly free for the first time was a triumphant way to conclude this project.

Sources:

  1. Jabr, Ferris. “How Does a Caterpillar Turn into a Butterfly?” Scientific American. 10 August 2012. http://www.scientificamerican.com/article/caterpillar-butterfly-metamorphosis-explainer/
  2. Hoskins, Adrian. “The Butterfly Lifecycle.” Learn About Butterflies. 2014. http://www.learnaboutbutterflies.com/Lifecycle%207%20-%20chrysalis.htm
  3. Nielsen, John. “Study: Moths Can Remember Caterpillar Days.” National Public Radio. 10 March 2013. http://www.npr.org/templates/story/story.php?storyId=88031220

Categories: science