Use your goggles to shoot the gnawing lurkers was a mission in The Precursor Legacy that Jak and Daxter completed to obtain a power cell. Gordy commented how Lurkers had been eating through Spider Cave's support beams and asked Jak to take care of it.
Walkthrough[]
When you enter Spider Cave, you'll notice a number of support beams, tall wooden logs, that have been infested with gnawing lurkers. With mostly one or two lurkers per beam, every lurker has to be killed and the last one will drop the power cell. It's impossible to harm the lurkers with melee attacks, since as soon as you even encounter one within your range, it will be scared off and retreat back into its support beam.
Instead you'll have to rely on three yellow eco vents placed high up on ledges next to the walls surrounding the support beams. Having located a vent, simply use your goggles (
) to aim and shoot down the lurkers manually. The yellow eco will more or less automatically hit the lurker if it's coming directly at it even if the support beam is in the way.
It's recommended to carefully search each support beam for lurkers until you're certain it has been wiped clean. Eventually you'll have gotten all the ones from that specific vent and will have to find another and repeat the hunt from there. When you've gotten the last one, it will release a power cell (seen in a cutscene). If you can't find the last couple, it means you might need to search the support beams up close in case you missed one by chance.