I have also raised Swallowtail butterflies from eggs found on parsley in a fashion similar to that described here. I would be interested in hearing about the experiences of other readers in locating and identifying the eggs of other types of butterflies.
Step 1: Timeline
June 28 -- Monarch butterfly observed laying eggs on milkweed.
June 30 -- Five eggs brought inside (photos only show four).
July 2 -- Transfer eggs to a fresh leaf in anticipation of the eggs hatching.
July 3 -- Two hatched by early morning and the remaining three by noon.
July 5 -- Colored bands becoming apparent.
July 8 -- Getting bigger.
July 12 -- Lost one caterpillar. Failure to thrive.
July 13 -- Start molting period. Appear uninterested in food.
July 15 -- Finish molting. Voracious and big.
July 17 -- J-hooking.
July 18 -- Four chrysalises. Nothing left but the waiting.
July 28 -- Chrysalises darken in the evening. Wing patterns clearly visible.
July 29 -- Butterflies emerge!
Step 2: Milkweed
Milkweed has wonderful flower clusters that attract butterflies. I grow a patch outside my kitchen door. My neighbor grows a lots of flowering plants and I believe his flowers attract butterflies and then they come on over to lay their eggs!
Step 3: Monarch Eggs
Because my milkweed patch is right outside, I have been fortunate enough to see the butterflies actually lay the eggs. The female (without the spot on the wing) lands on the edge of the leaf, curls her abdomen under the leaf, and touches (I assume) her ovipositor to the underside of the leaf. An egg is laid!
After locating several eggs, pick the leaves and store them inside on a plate. The leaves will dry out and curl up. Dried leaves will not provide food for the baby caterpillars, so you have to be prepared to move them (the eggs and later on the caterpillars) from dried leaves to fresh leaves. See details in the next step.
Step 4: Hatching
This technique of transferring the eggs and caterpillars onto fresh leaves will be used throughout the entire process. It is much better (for the caterpillars) than trying to slide a knife under them or otherwise dislodge them from a dry leaf in order to move them onto fresh food.
Step 5: Close-ups
Step 6: Baby Caterpillars
Caterpillars move around. Sometimes they are happy on top of the leaf, sometimes they prefer the bottom side. Occasionally they leave the leaf. In any case, it is important to keep track of how many caterpillars are in your care. When it is time to transfer them to a new leaf (see next paragraph), carefully pick up the leaf and make sure all are accounted for.
As the fresh leaf dries, it is necessary to transfer to baby caterpillars to fresh leaves. When you are ready to do this, locate each caterpillar and carefully cut around each. Transfer the small pieces onto a fresh leaf. The caterpillars will not linger on the dried piece and will seek out fresh food. This is the same technique described in the Hatching step.
Step 7: Growing Up
Use any jar that is relatively large and easy to clean (they poop a lot). I use a one quart wide-mouth canning jar because it is easy to get old leaves out and new leaves in. Cover the lid with a paper towel (more on that later) and poke some air holes in it. When you clean the jar, be careful to dry it thoroughly. Monarch butterfly caterpillars that fall to the bottom of a jar into even just a bit of water do not recover. Keep them dry!
Step 8: Molting
Step 9: Vacationing
Step 10: Forming the Chrysalis
Once the chrysalis is formed, there is nothing left to do but wait. If I am lucky, they form their chrysalises on the paper towel that I put at the top of the jar. This seldom happens. In any case, I usually transfer them to a net enclosure so the can fly a bit when they hatch.
Step 11: Emerging from the Chrysalis
When the butterfly emerges, its wings are very small and its abdomen very large. Watch carefully and you can see fluid pumped into the wings. They expand considerable and in a short time achieve their full size. Also, the emergent butterfly will flex and extend his/her proboscis. It is usually curled up but is surprisingly long.
It happened when I wasn't watching and I didn't get any pictures :-(