Milkweed plant CHRYSALIS egg photo metamorphosis chorion prolegs nine months growth cycle egg See Instar Identification Guide nine months Milkweed plant University of Minnesota adult Source Fourth Instar prolegs larva (caterpillar) instars pupa (chrysalis) CHRYSALIS The University of Minnesota instars nine months Monarch Caterpillar egg photo metamorphosis metamorphosis prolegs egg photo CHRYSALIS Milkweed plant Fourth Instar University of Minnesota's monarch site instars "Monarch Life Cycle" Monarch nursery