In 1669, Malpighi published the first systematic dissection of an insect. The manuscript of this work contains a striking water-colour of the silkworm, which is described here for the first time. On repeating Malpighi's pioneering investigation, Swammerdam found what he thought were a number of errors, but was hampered by Malpighi's failure to explain his techniques. This may explain Swammerdam's subsequent description of his methods. In 1675, as he was about to abandon his scientific researches for a life of religious contemplation, Swammerdam destroyed his manuscript on the silkworm, but not before sending the drawings to Malpighi. These figures, with their rich and unique use of colour, are studied here for the first time. The role played by Henry Oldenburg, secretary of the Royal Society, in encouraging contact between the two men is emphasized and the way this exchange reveals the development of some key features of modern science - replication and modern scientific illustration - is discussed.