How the Snake Lost Its Legs fly embryo. His books on evolutionary developmental biology (evo-devo) include "Imaginal Discs: The Genetic and Cellular Logic of Pattern Formation" (2002), "Quirks of Human Anatomy: An Evo-Devo Look at the Human Body" (2009), and "Deep Homology? Uncanny Similarities of Humans and Flies Uncovered by Evo-Devo" (2017). In Held's view, "Quirks", "Snake", and "Deep Homology" form a trilogy on evo-devo. "How the Snake Lost Its Legs" is ostensibly organised into six chapters, but in effect into three parts. The first chapter serves as an introduction and overview. The next four chapters provide what Held calls "the meatier aspects of evo-devo" with
Apollo (butterfly) favourable conditions for the butterflies, which share their grassland habitat with sheep. For example, grazing periods have been shifted to avoid the Apollo butterfly larvae stage, which is vulnerable to being trampled. The Apollo butterfly has many subspecies around the world, and some European subspecies are showing an alarming decline in numbers. This is mainly caused by habitat destruction, air pollution affecting the insect's food plants, and butterfly collectors. The Apollo butterfly is also more vulnerable to predators as it spends two years as a caterpillar. Apollo (butterfly) The Apollo or mountain Apollo ("Parnassius apollo"), is a butterfly of the