英语听力文摘 English Digest 632 昆虫是如何对抗细菌和寄生虫的？

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　　Imagine that you’re an insect, and that you’ve fallen ill because some bacteria or parasites have invaded your body. If you want to make it to a ripe old bug² age, your body will need to fight off these invaders⁴.

　　Invaders

　　The problem is that if you’re a bug, your life span may be only a few days long. This means that unlike humans, you simply don’t have the time to lounge around in bed, watching TV and waiting for your body to figure out how to fight off each disease it encounters.

　　Still, there’s no reason for your insect self to panic. Evolution has provided you with what scientists call innate⁵ immunity⁶, which you inherit from your parents. Innate immunity means that your bug body has the capability⁷ to instantly recognize and destroy many dangerous intruders.

　　Here’s How Innate Immunity Works

　　In your bug body there is a fluid called hemolymph, which is equivalent to human blood. If you’re injured, components⁸ in the hemolymph interact with specialized⁹ cells in your immune system to clot¹⁰ and form a scab that seals off your wound and prevents infection. The hemolymph also contains proteins that are ready to kill invaders like bacteria or fungi¹¹. However, some invaders, like tiny parasitic¹² insects, may be too large for the proteins to handle.

　　In this case, your body encapsulates the invader³ and walls it off from the rest of the body. The encapsulated invader then stays inside you for the rest of your natural bug life, or until you fly into a windshield, whichever comes first.

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