That's been my experience also.

I just bought a fly trap at Home Depot - it works great.

Ditto for me. I'm always reading about and seeing pictures on this forum of butterflies eagerly feasting on bananas and various mixtures to attract butterflies like red-spotted purples and question marks, but my rotting fruit only gets flies, too.
I don't know why - there are plenty of red-spotted purples here. Maybe it's because I'm out in the country where there are lots of cows and horses and other critters making lots of poop and an occasional dead carcass, their favorites! :/
Sherry

I've had the same experience with the banana "slop". I think in the 3 years that I put it outside I only ever saw a butterfly on it TWO times, a Question Mark both times. It did really attract the flies though and some kind of huge wasp (sort of resembles a yellow jacket only bigger), neither of which I want here, so I have given up on the banana thing. I guess some people have luck with it and some don't for whatever reason.
Cathy

I had these butterflies (there are 4 of them) come for overripe banana, but there were some flies too. It is at the outside edge of the garden, so I didn't worry too much about the flies. The banana was very overripe.

I haven't repeated it but probably will if I have some more rotten fruit.
kay

Sherry, I don't know. I have been making a regular circuit where the cows rest and do their thing, and I've yet to see a butterfly on them...maybe Okie butterflies just can't quite get it right.

Anna

Ripe bananas, dark molasses, dark rum.... works!!

Also, try plums, nectarines, cantelope, watermelon, sometimes I put out apples or apple sauce.

Hmmmmm. Velly strange. I get tons of butterflies on my fruit feeder - along with flies, fruit bugs, fruit flies, you name it. But, nothing stops the butterflies from having a meal.

This has been a really good year for fruit production in Oklahoma, so maybe a lot of the wild fruit trees have lots of rotting fruit around them for the butterflies. I don't use anything but fruit - I mean, I don't mix up anything with beer, molasses, or whatnot - and yet they still come. I would guess they are getting their meal elsewhere as MissSherry suggests.

Susan

I found this file that has plenty of suggestions on offering fruit and a mixture of other things sweet.

Here is a link that might be useful: Can I attract butterflies without gardening?

I guess if I'm going to reference a picture I should post it, sorry.
{{gwi:500646}}

kay

That's a great idea, sand, salt, and a bit of fruit.

You must have a Hackberry tree close by.

Rather than fruit, you could also try some powdered egg white in the sand/salt mix. Some butterflies are really attracted to proteins (hence the poo!). A very small amount is needed.
-Elisabeth

You should also make sure your fruit is wayyyyy overripe, as in virtually rotten. This is what they absolutely luuvvvvv.

Kay, looks like you've got a Question Mark and a Hackberry Emperor there enjoying the meal.

Susan