Gjall. Garbage near useless drop and @ 1,500 HP with the ability to fly and deal heavy damage to structures they are just menaces.

The Ticks are more valuable than them as the Blood Clots are used in some good stuff—sometimes I'll leave a Gjall alive for awhile just to farm more Ticks for Blood Clots.

EDIT: the AI thing where they run around you for a bit is to actually make them easier to fight as it prevents them from aggressively attacking you nonstop. You'll find the same with the Fulings—they attack then run a bit to give you breather. Annoying if it is just 1 or 2 but can save your life if you pull a swarm of them.