These look like a cross between a piece of grass, a mantis and a stick-insect. Ranatra species are predatory and rely on their resemblance to aquatic weeds to ambush small, live prey. They do fine in any kind of fresh water, but require a floating platform (like a stick) to hold onto. They breathe through the end/tip of their abdomens and will hold onto the platform to make this easier.
Rarely available. $12 each. Live guarantee with express mail only.
Bugguide.Net has photos here.
- Item #: bic925