Build a fruit fly trap out of a 2-liter plastic bottle and some rotten fruit! Fruit flies are easy to catch in warm weather. Once you catch some, you will be able to see their life cycle up-close. Watch carefully: they're tiny, it happens fast. The females in your trap will lay eggs, and in a few days they'll hatch. Watch for the different stages - eggs, larvae, pupae, fruit fly. The entire life cycle only takes about 2 weeks. Check out the Bottle Biology link for more activities to make with your 2-liter bottle.