This coprolite looks very similar to those produced by some modern caterpillars. The shape of caterpillar poop depends upon the shape of their intestine. How Caterpillars Work has a wonderful image of a caterpillar digestive system.
This piece of amber also includes some stellate plant hairs (the little star shaped plant fibers), and a flying insect covered in a white milky substance. What is the white stuff? I could be some sort of entomopathogenic fungus. This type of fungus infects insects while they are still alive, slowing killing it's host as it feeds on it. YUCK! If I had to pick a way to go, it definitely wouldn't be eaten alive by a fungus!
ANOTHER FUN FACT: Caterpillar poop is also know as frass.