The adult leaf-footed bug in the pics kinda gives it away. It's the big brown one looking at us in the top right of the first 2 pics. Too bad, those things are annoying. The first few instars of leaf-footed bugs and assassin bug nymphs are very hard to tell apart. Eventually the little wing nubs become more obvious on the assassin bug nymphs. The clustering behavior is not a sure fire way to tell. I had a mild outbreak of aphids the last 2 years and also a healthy crop of assassin bugs. The ready food source tempted a whole bunch of the assassins to hang around, probably a dozen or more climbing all over my goat weed peppers. My own little pest control army.