Don't forget the the, uh, pink widows? _Rosencrantz_ ("they're pinkish and make you dead, like him and Gildunstern"). Venemous ambush predators, low density (mostly made of this aeogel with hydrogen bladders). About an inch across and 8 inches long, like pink hovering snakes. They float, hiding in the exhalation contrails, waiting for prey to blunder into them.