Why Is It?
Cicada Cycles
Why are cicada cycles always prime numbers? (Prevents specialist predators from developing)
Cicada Emergence
How do cicadas know when to emerge? (Don't know -- might be sensing something in tree sap)
Bug-Eating Plants
Why do some plants eat bugs? (They live in nutrient-poor habitats; bugs have lots of nutrients.)
Twinkling Stars
Why do stars twinkle? (Atmospheric turbulence bends the light, and our pupils are small.)