We put out some orange slices for birds, mainly Baltimore orioles, in the spring. They were put out every few days in the spring. Then in late June, the orioles quit coming to the fruit. It is still out there, up high near the bird feeders, but now it is attracting butterflies.
These northern pearly-eyes were there last night about dusk.
This morning it was a little more diverse. There were red-spotted purples, hackberry emperors, tawny emperors, northern pearly eyes, and eastern commas.
The butterflies are relatively docile and allow you to get close (although I needed a ladder to get close to these guys). This is a red-spotted purple.
This is an eastern comma.
Rotten fruit is great for attracting butterflies, but it will also attract insects you might not want as well.