I have always loved that when they mate they create a heart shape. Amazing creatures.
How to Draw Blood, text, types of blood; How to Draw Manga/Anime
ArtStation - retired, Park Pyeongjun
An illustration from Jules Verne's essay "Edgard Poë et ses oeuvres" (Edgar Poe and his Works,1862) drawn by Frederic Lix or Yan' Dargent.
Les vapeurs de la nuit, 1896 ~ by Yan’ Dargent