Spider mites do not normally eat leaves or holes in plants...rather they suck and feed off the chloryphll from individual leaf cells.

They can be spotted by a pattern or looking like salt was sprinkled on the leaves...little white spots.

The webs could be hosts to spiders predating on some other type of insect who is eating your plants, and killing off the spiders could be the last thing you want to do.

The only way to tell for certain is to take a leaf that has been damaged and look at the underside of the leaf with a power lense or scope.

Spider mites generally are translucent when juvenile and then get brown patches...they have red eyes...they leave little black shit on the leaves, and they lay perfectly round balls or eggs.

They look just like a trich...without the stalk!

Whatever you are trying to kill, if there are eggs, you will need to reapply every 4 days for 21 days.

Saturate the ENTIRE LEAF. Each and every single one. Every 4 days.