A 'ginger bug' is not a red insect. Beyond that, the clearest and most efficient way to help you understand what it is is to instruct how to make one.
- Get some fresh ginger. You can rinse it off a bit if you must, but don't try to scrub it clean. Trust nature.
- Grate up a few tablespoons, skin and all. Yes, skin and all. That's critical. You could also slice it really thin.
- Put the ginger in a mason jar or similar wide-mouth glass container together with a tablespoon or so of sugar and a cup or so of water and cover it with a piece of cheese cloth. I just put the lid on very loosely.
- Place the jar in a cabinet or other dark warm place to ferment.
There. You have started a ginger bug, a culture of natural fermenting microbes that are growing in a mixture of grated ginger, sugar, and water. This is like a sourdough culture in that it relies on yeast and bacteria that occur naturally on the unpeeled ginger and in the air to ferment the sugar.
In a few days you should see some bubbles and some sediment. That means your culture is alive and well. If it isn't working, you may have used ginger that has been irradiated to kill the needed microbes. Or you may have used chlorinated water, in which case you should boil it to remove as much of the chlorine as possible.
You can name your ginger bug and 'feed' it every day or so by adding more ginger, sugar and water. Once it's going well, you can put it in the fridge to sleep until you need it.
Q&A
Q: Yeah, so what use is a ginger bug?
A: To make ginger ale, ginger beer, or other lightly fermented juice drink.
Q: Why do they call it a 'ginger bug'?
A: I have no idea. I asked the Intarwebs, but either no one knows or they ain't sayin'. If you find out, tell me.