Prima vēna

The Annotated Budak: Prima vēna by @budak

Five primary veins – costa, subcosta, radius, median, cubitus and anal – sprout from the backs of dragonflies to create a framework for flight with few peers in the arthropod world. The first terminates at the tip, near which a drop of pigment confers a stabilising weight to each stiff wing. The second ends where the leading edge hits a notch, its duties cut short by the need, perhaps, to strengthen the base of odonate propulsion. The third and fourth veins begin as conjoined twins but soon separate, with the radius giving rise to lines that support the distal margins of the wing and the median fronting a juncture of odd-shaped cells that betray the prehistories of these aerial hunters. The final two wind through the rear, with the anal vein running parallel to the cubital in damselflies but tracing a sock-shaped loop in advanced libellulids. Zygoterans, save the demoisell...

Full article: http://budak.blogs.com/the_annotated_budak/2012/06/prime_...