Headlice can't jump... they don't have any knees!
Their instinctive survival drive to stay on a human head is strong; once it's off the scalp and loses access to a blood meal, it will starve and die within 8 to 12 hours.
Headlice claws have evolved to fit neatly around a single strand of hair and the curvature of it is close to the average hair diameter that they would come in contact.
However, the claw has one more very special feature... it is equipped with an internally facing barb/spike that pieces the hair fiber like a spear.
This action of clasping and piecing the hair strand simultaneously with every one of its six claws gives the louse serious staying power!
With its tight grasp a hair strand, it can swing or crawl from hair to hair like a speedy acrobat... think of a Trapeze Artist at the circus... holding on with one claw whilst extending full-reach with the other.