Flashfly Cage is a Palico Gadget in Monster Hunter World (MHW). Palico Weapons all have a Melee and Ranged value as well as a Blunt or Severing Attack Type. Unlike human weapons, you cannot upgrade their Palico counter parts.
"A Palico gadget that stuns monsters with a flash of light. They can use this more often as their proficiency increases."
How to get Flashfly Cage
This Palico Gadget is obtained by completing the Grimalkyne sidequest in the Ancient Forest.
You can begin the sidequest by traveling to the top of the Ancient Forest with your Palico in tow. In the maze of vines and pathways behind the Rathalos nest, you will encounter a lone Grimalkyne, who will run away from you. Follow him all the way to his encampment, and he will reward you with the Flashfly Cage.
Use and leveling
Once aquired your palico will set down a flash cage to help stun monster.
At gadget level 5 palico will also start using a make shift electric trap. Duration of trap is not as long as shock trap used by hunters.
Once palico has reached gadget level 10 you will be able to command palio to use either trap on command with a regular cool down time.
In Iceborne, the flash fly cage gets a new equipment piece called the boombug cage and can be used a proficiency level 11 and up. The boombug cage acts like the thunderbug cage where your palico sets down a trap for a monster to activate. When a large monster walks over the boombug cage, the trap will explode dealing around 100 damage to the monster and staggering it. It can’t activate on monsters flying in the air over the trap.
Once the Palico reaches level 15 proficiency, you can now use the trap on command. It will still have a cool down like the rest of the Palico gadgets.