How long do those caterpillars live?
They (the Black Swallowtail) grow relatively fast. Its amazing how big. they get day to day. Maybe a couple of weeks (2-4) until they form a chrysalis. Then another 2. - 3 weeks until they emerge from the chrysalis as. a Butterfly. Im sure it varies for different types of butterfly, the black swallowtail is the only one im familiar with specifically.
The small caterpillars are mostly black with a single thick which stripe/ band somewhere in the center. (The almost look like bird crap, which may be a camouflage/ defense thing, not sure). As they. get older they develop their stripes.
If you touch them, or they feel threatened , they have these yellowish orange (2 of them) extensions that pop out of their head ( and give off an unpleasant aroma). They almost look like horns, but are soft, not hard.
I actually had one that formed a chrysalis, but way too late in the season, so I stored it in my. fridge, and when spring time. came, I took it out and it ' hatched'. I dont think they migrate like monarchs, but overwinter, or kinda hibernate until the climate is ideal. The kids loved. watching them change.