Can’t quite bring myself to keep birds as pets but for some reason keeping butterflies in a cage seems more humane. The idea of having a large outdoor cage to walk into filled with tropical butterflies seems highly improbable but intriguing.
I once Googled up how to breed butterflies but the best thing I found was a website telling me to pile leaves and rubbish in the corner of my garden to encourage butterflies to breed there.
Any ideas?
PS is it just me or are there far less butterlies around then when I was a kid 30 years ago? Are pesticides killing caterpillers?
Butteflies don’t live very long, unfortunately. Most mate, lay eggs, and die within a couple of weeks.
I did hear somewhere about kits you can get for little kids, though, where you raise a caterpillar in a little terrarium and watch it pupate. One place to get 'em.
You can plant your lawn with plants attractive to butterflies, though. Some tips.
My daughter had a similar kit and to my surprise all 5 caterpillars actually lived and metamorphed into Butterflies. After 3 days she released them outside.
She then found a Chrysalis on the ground early September and brought it home and it metamorphed into a Butterfly in January. Unfortunately we couldn’t release it and it only lived a week inside the small Butterfly home.
As Podkayne suggests, most butterflies do not make good candidates for pets those who get attached to them, since the usual life span of adults is a matter of a week or two. Some Monarchs may live 8-9 months, but will spend much of that time dormant. The tropical Heliconius butterflies may live quite a few months. “Butterfly Garden” exhibits at zoos and museums keep a stock of pupae on hand which are constantly “hatching” new adults to replace the ones that die.
If you really want to have an insect for a pet, I would suggest getting a young nymph of the 17-year Cicada. 
My uncle is a butterfly freak, and I suppose you could say he has butterflies as “pets”…they even live in his house
I’ll tell you some of the things he does that I can remember off the top of my head…
- Everywhere he goes, he looks for catepillars, and takes them home in a container. Then I suppose he releases them into his yard…
- Of course, he knows which catepillars turn into which butterflies. Some turn into moths, which are ok because some moths are very pretty.
- He encourages cocooning in his catepillars. Not sure ho he does this BUT whenever a coccoon ends up on one of his trees (his smaller trees), he covers the branch in some sort of netting, to keep the coccoons from being eaten. And then I suppose once they hatch …he’s got a captured butterfly.
- He’s got some sort of hut that he constructed out of aluminum flashing and old scraps of wood. I assume he keeps his captured butterflies in there so they lay eggs for him.
- He has plants in his yard which attract butterflies. I don’t know the specific plants, but he does have butterfly bushes and also Mimosa trees (yeah, even up here in NE Ohio. Dude has a green thumb…) You can go to his house any time when butterflies are “in season” and see them on his plants.
- I think he occasionally buys catepillars or butterfly eggs online. No idea where or how. Or maybe he’s part of some butterfly fancier’s messageboard and they trade eggs and catepillars.
- For some reason he keeps a lot of his catepillars and cocoons inside. Usually in mesh wire trash cans with books over the top. No idea why these are indoors and others are outdoors.
It looks like there’s a lot of butterfly enthusiast sites out there, you should check them out. Maybe google “butterfly garden”. Like others have said they don’t live long but there’s things you can do to keep your “butterfly cage” stocked - got to remember that butterflies aren’t always butterflies, they’re sometimes eggs, sometimes catepillars
Here’s a list of butterfly gardens. My girlfriend went to one in Wisconsin and she said it was beyond cool. If they can do it, I’m sure they could help you set up your own butterfly garden.
http://www.thebutterflyfarm.com/usa_public_butterfly_gardens.htm