IDed on BugGuide by Lloyd Gonzales via Roger Rohrbeck. We are ~0.5 km from the Raritan Estuary here.
An early spring species typically found near sandy lakes & ponds (as here, probably a couple hundred meters from Helmetta Pond).
Andy Hamilton says Ceresa lutea is "the common eastern 'hornless' species with dark legs", & confirms the ID on this specimen. On Bracken Fern in pine barrens understory. Seriously camouflaged -- apparently this sp. feeds on lots of other plants, but it sure looks perfectly designed to resemble one of the fern leaflets!