Since butterflies can’t chew their food, they need to drink the juices. Fruit that just ripe or fruit that is starting to get mushy is the best to keep in your feeders. When it comes to feeding butterflies, the softer the fruit, the easier it is to eat. Butterflies aren’t picky when it comes to the fruit you leave out. Some commonly used fruits are watermelons, bananas, pineapple, oranges, and peaches. Experiment with different fruit to see what species you attract. A butterfly proboscis can’t penetrate the thick peels of fruit. Use a sharp knife to slice the fruit open so the inside flesh is easier to eat and drink. In case the fruit still isn’t easy for a butterfly to eat, making multiple slits in the flesh of the fruit gives a space for the juice to collect. Using the same knife as before, make shallow cuts into each piece of fruit you’re leaving out. You can also scrape the fruit or stab multiple holes into it with the tines of a fork for a similar effect. Fruit left out overnight may attract raccoons or other destructive mammals to your yard. Store fruit in a cool place like a garage or shed overnight and put it back in the morning. As the fruit keeps rotting, it will get softer and easier for the butterflies to eat.  Replace the fruit once the fruits have turned black or moldy. If you save the fruit, cut 1⁄8 inch (3.2 mm) into the fruit with a knife or fork each day so there is easy access to the juices.

Summary:
Pick fruit that is ripe or overripe. Cut the fruit into quarters to expose their flesh. Make slits in the piece of fruit so the butterflies can get the juice. Move the fruit at night to prevent unwanted pests.