youngs and eggs hatch into caterpillars. they feed exclusively on the milk weed which has been eliminated. and now these animals lost a breeding site. with the increase of traffic, climate change and other issues is why they are disappearing. >> why has it been getting pulled? >> well because it's kind of looked as a pest milk swede very large weed. it's a very common -- it really can overtake a garden if you don't manage it. but in the natural world it really is instrumental to the survival of these incredibly beautiful and he could logically important butterflies. >> these butterflies are like amazing. they go -- how many miles they go, right? >> well what's really amazing to me is their lifecycle. it's not one butterfly that makes the migration.