Roofus, that looks like a juvenile thrip,...definitely not gnat larvae-- they live only in the soil, snacking on roots, and look a lot like a maggot,... Are you seeing some light, almost silvery patches/spotting on the leaves, top and/or bottom? This is sign of their feeding; Thrips are very mobile, and adults can fly, so keep that in mind when searching for them, beyond just the plants themselves! Often, I spot the damage first, then hunt for the little butt-nuggets with a magnifier... they will evade you when you go looking! There are many sprays on the market that are effective on them,... I'm liking the results I get from products with Spinosad in it; this is a OMRI food safe bug killer, and leave minimal residue behind... Neem, pyrethrum, Azamax, are others to consider,... get aggressive with treating for them,... reapply a few days later, and keep watching! What you kill one day, may be replaced by others a short time later, until you decimate the population including hiders... are you outside?