That link doesn't open for me, but I looked up the name. I have trouble with leaf legged bugs
, a relative of the photo you found. You don't want to burn your tender plants so be careful with the orange oil and such. I'd knock them off with water and spray an orange oil mix around the base of the plants, or I'd do a foliar feeding and have a little orange oil in there along with the good stuff. Look in the library for formulas and times of day for that.
Actually, if you're made of stern stuff, just reach out and swat them or flick them hard with your hand. I usually wear gardening gloves for that. I have a couple of 1 gallon paint sticks from Home Depot that I use also - they get on plants like the jimson weed and I creep up with the sticks and with one above and one below, I pop them a quick one and they die. You don't want to smash your onions, but you might be able to flick them off, then treat the area around the onions. They're in that family of beetles like the stink bugs, so they have a kind of perfume smell when you swat them.