- 1The imago of Vanessa urticae has three Malpighian tubules on each side opening by a short common duct at the junction of the mid-gut and hind-gut. There is no rectal plexus or other complication of anatomical structure.
- 1The metamorphosis has three principal characteristics: (1) the destruction of the larval rectal plexus by phagocytosis, (2) the shifting forwards of the attachment to the gut with phagocytosis of the larval ileum and most of the larval common duct, (3) the persistence of the larval tubules into the adult phase with the break-up of the cell nuclei into many small nuclear bodies.
- 1This type of metamorphosis is fairly general throughout the Lepidoptera, but forms are known in which the larval tubules are destroyed and the imaginal tubules are new growths. In both the larva and imago of Hepialus humvii the tubules open into the alimentary canal at the junction of the mid-gut and hind-gut and there is no rectal plexus. The metamorphosis in the higher Lepidoptera may thus represent a reversion to a more generalized condition. It does not possess any apparent functional significance.
- 1The metamorphosis of the tubules in insects in general varies according to the growth activity of the posterior interstitial ring of the gut. This is correlated with their embryonic development, and perhaps with their mode of growth in young stages of the lower insects.