From "The Adventures of Tom Sawyer", what insect does Tom watch in church, during the preacher's sermon?

Tom actually watches two different bugs instead of listening to the preacher. In chapter 5, Tom "did not enjoy the prayer, he only endured it--if he even did that much." His attention is captured by a fly on the pew in front of him. He watches it throughout the prayer and just "itches" to catch it, but he doesn't dare during the prayer. When the preacher says, "Amen," however, Tom does grab the fly, but Aunt Polly makes him let it go.

The other bug is what Tom calls a "pinchbug," a large black beetle. After having to let the fly go and still bored with the sermon, he remembers that he has the bug in a box in his pocket. The scene becomes comical when the bug bites Tom on the finger, making Tom drop it on the floor. Other churchgoers begin to notice the bug, especially when a stray dog comes into church and decides to sit down right on top of the bug. That's such a funny scene, you'll just have to read it for yourself!