After eating the egg case the 1st instar caterpillar begins to eat the hairs on the milkweed leaf which also held it's egg. After the hairs the caterpillar will start to eat the leaf proper. This young caterpillar is not big enough yet to chew entirely through the leaf but within 24 hours of hatching that will be possible. In the next two weeks the caterpillar will eat the equivalent of 6-8 large common milkweed leaves.
As the caterpillar grows to become a chrysalis it will need to shed it's skin 4 times as it's body outgrows that skin. This caterpillar has just shed it's skin and will rest for about 90 minutes afterwards. As it rests it's head, feet and pro-legs will get the distinctive black and yellow coloration that is absent immediately following the molt. Notice the anterior tentacles are still folded back against it's body. These will slowly extend forward over the next two hours.
As with the egg case, the caterpillar turns and proceeds to eat it's recently shed skin to retrieve the nutrients in that skin. This will take place after each molt. The only thing not consumed is the molted head cap seen laying behind the caterpillar.
Photos by: Jeff Ormiston