caterpillars turn into butterflies -- 09/26/18
Today's selection -- from The Life Cycles of Butterflies by Judy Burris & Wayne Richards. Caterpillars turn into butterflies:
"Once a caterpillar has reached maturity, it begins to look for a good place to pupate, or enter the chrysalis phase. It stops eating and may empty the undigested contents of its gut. Sometimes it changes color. Generally, the caterpillar leaves its host plant and wanders away to find a safe place from which to hang. All sorts of locations may be suitable: A pile of wood offers good protection; the underside of a large leaf provides shelter from rain; a tree branch is an easy place to blend in. Sometimes the caterpillar spends several hours crawling around to find the perfect spot.
"After the caterpillar has chosen a place, it begins to spin a patch of silk that will be the anchoring point for the chrysalis. The caterpillar has a gland called a spinneret below its mouth that produces silk. By moving its head back and forth, the caterpillar can weave a mat out of silk threads. Using special clasping hooks on its rear end, the caterpillar then backs up and grabs the silk patch and holds on tight.
"In fact, its life may depend on the strength of its grip. If the soon-to-be chrysalis can't hang on through wind and rain, it will probably die when it hits the ground, bursting like a water balloon. If it survives the fall, a predator may eat it.
"We've discovered chrysalises hanging as low as a few inches from the ground on a plant stem and as high as six feet up on the side of a building. And when you have a garden full of host plants, you're bound to find chrysalises in some strange places. Last summer we found one hanging from the underside of a rocking chair on Wayne's deck.
"We couldn't let anyone sit in it until the butterfly emerged. We've found chrysalises hanging from deck rails and garden statues, as well as on sliding glass patio doors. We're now in the habit of checking everywhere for these surprise packages.
"After the caterpillar gets a good grip, it may hang upside down, as Monarchs do, or spin a silk thread and use it as a harness to support itself upright, as swallowtails do. Up to now, juvenile hormone has kept the insect in the caterpillar stage through each molt. Now that it is fully grown, production of this hormone has stopped, and the caterpillar sheds its skin for the last time, to reveal a chrysalis. The old skin splits first at the head, and the pupa wiggles and squirms its way out. When the skin has peeled all the way down to the rear end, the pupa must twitch violently to break the small ligament attached to the skin. Then the skin falls away like a stretched-out old sock.
"Once the chrysalis dries and hardens a bit, it gains some protection from the weather and small predators. Its dull coloration, usually shades of green or brown, helps it blend in among leaves and twigs. If this phase of its life cycle occurs during the warm summer months, the butterfly should be fully developed and ready for eclosion, or emergence from its chrysalis, in about two weeks. If the insect enters its chrysalis phase during the cooler months of autumn, then it may wait out the winter by going into diapause, hibernating until warmer spring weather arrives. Sometimes butterflies that emerge in the spring are smaller than the ones that emerge during the summer months.
"During the chrysalis phase, the caterpillar liquefies inside the chrysalis and reorganizes, almost magically transforming into a butterfly. Even after decades of research, all the details of this metamorphosis are not completely understood."