Thank you for the advice everyone. Although I found the four caterpillars on four different days, I did find them all in the same patch and believe they came from one butterfly or two butterflies that laid eggs at the same time. I found one on Thursday June 15th and he was tiny! I found the others on Monday, Tuesday, and Wednesday of the next week. Everyone was the same size as the others when I brought them indoors and they all formed chrysalises within 30 hours so I am guessing this is one group.
I am concerned because two of them are in a small cage and the second one formed his chrysalis an inch away from the first one. It looks like the first one may be ready to emerge soon.

It has been nine days and the chrysalis is getting darker and I can see the outline of his body. I dont know what will happen if he knocks into the other chrysalis when he emerges. I had bought a larger cage but it was too late to move the two caterpillars by then. The third and fourth chrysalises are at least six inches apart. I will have to find something suitable in case anyone falls. I have put a stick in one of the cages. I was wondering if that would work.
I have been keeping the smaller cage in the aquarium when I am at work with the door propped open and a stick inside that one as well. Tonight I found another caterpillar! He is now occupying the aquarium and yes, there is a mesh lid. The only problem is it doesnt lift off but slides. I have been checking four clumps of milkweed all within walking distance. I found this guy in the same clump of milkweed as the other four. He looks a little lighter than the other guys, if I am not mistaken. He is bigger than the first caterpillar I found but smaller than the others were when I found them. I would say that he has at least 3 or 4 more days to go before forming his chrysalis.
Okay, now for some more questions! Is it okay to line his cage with paper towels to make it easier to clean and keep the leaves on them? His cage being so much bigger is going to make it harder for me to keep clean. I still havent found the perfect cage. I had a bug zoo when I was a little child. To me, that was the perfect cage, but I can not find anything like that. It was plastic and the bottom was mesh and came off. Perfect for cleaning and when all the chrysalises were formed, I could just take the bottom off altogether. My little cage has a side door. The hermit crab cage is all plastic but the lid pops in place and I dont know how to get the lid off without breaking the cage. I can open and close the lid, but would have liked to be able to take it off. The aquarium is all glass with a sliding lid.
I like the pictures of the chrysalises hanging from the lids. I am not sure where to find something like that though. I dont have any jars, as was suggested. This really has been a problem! I am going to have to reread how the material was attached to help a monarch if it has fallen when emerging. Do they usually emerge in the morning? I thought I read that. Also, when is the best time to find caterpillars? I have found mine all in the evening, but that is because I was only out in the day once. The other times I went to get the caterpillars fresh leaves at night after work and most times found another caterpillar! I have never found an egg, wouldnt know what one looked like if it bit me! Now that I am reading more, I am thinking the eggs might be too fragile for me to try to deal with, even if I found any. I am having enough problems trying to find adequate containers for the caterpillars.
Some of the milkweed doesnt look too healthy. The patch where I found everyone looks wilted and the pink flowers at the top arent in good shape. The largest patch looks the healthiest. In answer to what other types of insects I have found, I see a lot of beetles, some red insects that I dont know the name of, a couple of spiders, a couple of yellow ladybugs, some really small insects, and tonight, my first tick.
I am wondering why some of the milkweed looks healthier than others. We have had a lot of torrential downpours the last week and a half so I know that it isnt drought. In terms of the rain, there have been several unusually severe thunderstorms in a short period of time. I was surprised to find a caterpillar at all tonight with the type of weather we have had.
Also, I am wondering if the butterflies in Wisconsin lay their eggs earlier than the ones in Pennsylvania or if they lay eggs at the same time? I always thought they just sort of migrated, laying eggs in different states at different times. The more I am reading, the more I am finding out how much I dont know!