Answer: Preying mantids will eat almost anything that moves! Sounds like your apple tree has an infestation of leaf rollers. These caterpillars will go away soon, and the damage they do to the leaves of the tree shouldn't adversely affect the fruit. If it were in my garden, I'd leave the caterpillars alone, knowing that predacious wasps and other beneficial insects will discover the population and take care of them.
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