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Show Butterfly's "Trunk" Is Explained by Delaware Scientist Newark, Del, Butterflies and moths uncoil their long pro-bosces, pro-bosces, or "trunks," on very much the same principle as that used in the toy paper "snakes" that startlingly dart into your face at carnivals. This simple mechanical explanation explana-tion of one of biology's most difficult diffi-cult riddles has been discovered by Dr. J. B. Schmitt of the University of Delaware. In Two Sections. A butterfly's proboscis is not a simple tube or pipe. It is made of two trough-shaped sections, held together to-gether at the edges, so that it "adds up" as a tube through which the insect can suck up flower juices. In each half, beneath the trough, there is a tube, closed at the outer tip, but communicating with the head-cavity at its base. Each of these tubes is filled with blood. Normally, Nor-mally, the proboscis is kept coiled by the pull of many short muscles, arranged diagonally. But when the insect is ready to feed, a valve closes at the base of each tube, preventing the blood from flowing back into the head. At the same time, certain muscles squeeze down on the base of the tube, like a hand on a rubber bulb. This puts pressure pres-sure on the fluid, which has nowhere no-where to go but out, so that It pushes out into the tube and straightens it out |