Identical to the strategy of rearing milbert's tortoiseshells and red admirals, use rubber gloves when handling nettle.  Place cuttings in bottled water.  Cork the opening with toilet or facial tissue; so that the plant goes through to the water; but caterpillars CANT!  Replace host every five days or so.  Make sure your lid either has holes or cut a hole out of the lid and place screen over the hole so that caterpillar frass will dry and not get your larva sick.