boomslang

"that undulate long the edge of touch"

Is that meant to be 'along', or is length the overriding issue here?
I'm tempted to suggest that you'd do better ululating here, though in view of your earlier humping (the snake that broke the camel's back), that proposition might just sound like *pants.
[*http://en.wiktionary.org/wiki/pants - for definitions, incl. UK adjectival usage]