Who is this mystery critter?

1. I can be as short as a finger or as long as a small pickup truck.

2. I have no arms, legs, eyes, teeth, bones, or lungs. Not much of a brain either. But plenty of heart and muscle.

3. All my kids are girls. They're all boys too. 

4. The scientist Charles Darwin said, "Without the work of this humble creature...agriculture as we know it, would be very difficult, if not wholly impossible."

5. You can buy my poop by the gallon.

Bonus clue: Here's what I finish: book, tape, earth, inch, and ring.

Click here for the answer.

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