157504 Swallowtail - Papilio machaon ssp. britannicus - larva. Wingspan 70mm. Iconic and unmistakable butterfly with mainly yellow and black wings; hind wings have blue and red spots, and tail streamers. Double-brooded: adults are on the wing May–June, and again in August. Larva is yellow-green with black and red markings; feeds on Milk-parsley. Restricted to a few fens and marshes in East Anglia, mainly in the Norfolk Broads; easiest to see at Strumpshaw Fen and Hickling Broad.