This Cholla cactus field, for example, has a few surprises for the unwary hiker.  The friendly-looking, fuzzy cactus drops its ball-shaped branch tips all over the ground.  Anyone passing by who steps on, or brushes past a Cholla ball finds they will adhere to anything.   What looks like fuzz is really a dense network of spines.  Each spine has backward-facing barbs that first pierce, then hook into anything they touch.  Cholla spines easily go right through even the thickest leather boot.  If one mistakenly kicks a Cholla ball, it first adheres to the boot then the opposite leg on the transition step.  

It is this second state (adherence to the leg) where one become aware of one's mistake.   The number of spines per square inch stuck into the dermas is enough to traumatize the affected area of the skin into numbness.  Your first reaction is to gingerly grab the ball to extract it from your leg.  Then you learn interesting fact #3, it won't be extracted from your leg easily and you now have your fingers attached to the Cholla ball, which in turn is still attached to your leg.

Enter the magic extraction tool... the common comb.  Sometimes, the Cholla ball is stuck into the skin so firmly that it takes two people to extract it, one on each end of the comb.  It's insert comb between skin and Cholla ball, pull until extracted.   ...But watch out, the Cholla lets go fast once the backward facing barbs tear through the skin.  And unless you're really fast, the Cholla ball will fly through the air and stick to the rescuer, just like one of those Velcro darts to it's felt target.  

Fortunately, on this trip, attacks of the jumping Cholla were few.  Everyone at one time or another experienced the pain of defeat at the quills of this desert vermin.   I got one stuck in my left wrist, but was mostly save by my watch band.  Took only one person manning the comb to remove it.  A non-serious amount of blood was donated to the desert.