Two Truths, One Lie

Which fascinating fact is actually a fib?

1. A stonefly’s diet is made up partly of sand. This makes their outer shell extra hard, which is why they’re called “stoneflies.”
2. To get a girlfriend, a stonefly taps his belly on rocks and branches. If a female likes what she hears, she taps back.
3. Some stoneflies crawl out of icy streams in winter. Special chemicals in their bodies keep them from freezing.