十万个为什么·科学阅读30篇（1）
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Why Do Some Insects Walk on Water Without Breaking the Surface?
为什么有些昆虫能在水面上行走而不破坏水面？
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Water striders and other pond skaters stay afloat thanks to surface tension—the skin-like film formed by hydrogen bonds between water molecules.
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Their long, thin legs spread weight evenly and are covered with microscopic wax-coated hairs that repel water.
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This hydrophobic coating prevents legs from piercing the surface, letting them rest on top like tiny rafts.
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Even raindrops hitting nearby create ripples they sense instantly with sensitive leg receptors.
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They move by pushing sideways against surface tension, not by paddling downward into the water.
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Scientists mimic this design to build micro-robots that clean oil spills on calm water surfaces.
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If water is polluted with soap or alcohol, surface tension drops and insects sink immediately.
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This ability works best on still ponds—not choppy rivers—because waves disrupt the delicate force balance.
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Evolution shaped these legs over millions of years to exploit physics rather than fight it.
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Watching them glide reminds us that nature solves problems using forces we often overlook.