This caterpillar is awaiting its metamorphosis into a monarch butterfly, a stage which lasts anywhere from two weeks to one month. During this period of transformation the insect spends most of its time eating the leaves of a single plant, as it may grow in size more than 30,000 times. It also outgrows and sheds its skin several times during this process.
Links:
[1] http://www.smdailypress.com/sites/default/files/Paula's caterpillar CLR.jpg