I agree with Seamaiden in that it has the same shape as a box elder but not the right color. Could be a type of stink bug. Either way, not a beneficial so get rid of it. Stink bugs are not as damaging to vegetation as they are to fruit but will lay egg clusters on the bottoms of leaves of any plant and quickly multiply in numbers since there don't seem to be too many(if any at all) predatory insects that will eat them. And yes, I would be looking at the bottom sides of those leaves closely for spider mites!
on that it may be some type of boxelder beetle or something of that nature i would physically remove it, if you kill them inside they secrete a pheromone that attracts others...
Thats textbook thrip infestation on lower leaves. Got em myself as of late. They ars some bastards but not too hard to control if you get on it. And that bug could be a minute pirate. If it is leave it. But you best find out for sure.
The bug in question has several versions, some eat other bugs, but all of them eat leafs as well. Any time I notice them I also notice chunks bitten out of my leafs.
Not a box-elder, some type of stink-bug.
Box-elder's specialize in eating essential oils BTW.