A plastic sheet can be used in collecting to prevent smaller arthropods that scurry or leap from getting away. They are easy to see and capture on the plastic. I find it a big help when looking for a beetles and springtails in mushroom patches like these that sprouted in my front yard for instance. I just use my hands like a steam shovel and quickly uproot and deposit a bunch of mushrooms onto the middle of the plastic where I can then thrash them around or break them apart without worrying about escapees.

(These mushrooms will contain far more species in another week when they are a yucky, swishy mess so I left those I uprooted alongside one undisturbed bunch to draw in the critters.)

Other uses of plastic sheeting include spreading under an elevated log you plan to strip looking for underbark specimens or under a plant or bough you intend to shake. I have employed the method with animal carcasses, whose visitors typically scurry away into soil and litter. I just drag the carcass onto the sheet and flop it around, watching for fleeing carrion species.