You can extract arthropods from leaf litter by putting some on a mesh or wire frame and placing that midway down a collection container. Then shine a bright light from above to heat the top. The light can be strung through the top of the container (to keep it sealed), or the container can be transparent on the top. Or a funnel can be used to hold the leaf litter with the bottom hanging in a bottle. With no cap, more will escape than otherwise would, of course.
If you take too much litter you get a lot of bugs and it’s therefore not exactly harmless since you don’t know where they came from to put them back. But plenty of them seem to live, so it is not maximally destructive, either, and you can scale it down to as much litter as fits into a large funnel. You do need to get a good amount litter to have a chance of finding something inside it, since you get what migrates downwards from the light, so sample with that in mind and you’ll be good.
The setup is called properly a Tullgren funnel, so you can look it up. It grabs spiders, beetles, beetle larvae, springtails, millipedes, anything that lives in the soil and leaf frass.
If this fails, hit the bush with a sturdy, long-handled net. Then carefully inspect the net, not letting the fly out till you’ve seen them. This will harm a bush which is not sturdy itself: use judiciously.