I found what had been attacking my barrels due to the fact that they are now at my lithops. They are like small white dots when on the plants. When older they can cross the soil, rice shaped at this stage (very small), and I believe that they may finally become air born. Any way they turn the succulent to mush. There are small, closed, ulcers where they begin to eat the plant. It looks like the plant becomes sunken in. Mostly this occurs at the soil surface, but can start higher up the plant. I hit them with a pesticide/fungicide combo and hope it will work. I am going to change the soil after work tonight. Any idea what these are?