Monarch butterfly caterpillars are fun to raise until they form chrysalises and ultimately emerge transformed as butterflies. This instructable takes you even further back in the butterfly life cycle and describes how to raise a monarch from a newly-laid egg into a fully grown butterfly.
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
Below are the dates on which significant events in the life of these Monarch butterflies occurred. The timing may vary, but it will be helpful to know about how long things take.
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!