It's a stunt worthy of Houdini: A homely caterpillar ducks into a chrysalis and emerges a resplendent butterfly. Now, scientists are laying bare the caterpillar's magic. Researchers used a souped-up CT scanner—a version of the same technology that allows doctors to locate tumors and internal injuries—to peer inside the chrysalis of the painted lady (left image), Vanessa cardui, one of the world's most widespread butterflies. To create a single image, the scientists hung a chrysalis inside a drinking straw and slowly spun it while taking nearly 2000 x-rays. The result is a series of highly detailed 3D portraits of caterpillars as they transform themselves into butterflies, such as this image (right, with digestive structures in red) of a butterfly about to break out of its chrysalis. The method reveals new details, such as the unexpectedly early appearance of parts of the adult respiratory system, the team reports online today in the Journal of the Royal Society Interface. The researchers say that their technique could shed light on the development of a wide variety of insects. Potential applications include studying whether pesticides affect the development of bees, which are in sharp decline in many regions, and how genetic manipulation affects the development of the widely studied fruit fly.
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