Twit may have another suggestion, but I go with pretty safe and organic methods of bug control. For both these critters I use a couple of drops of dish soap or Safers insecticidal soap and a couple of drops of cooking oil in a quart of water in a spray bottle, shake well and spray. Try it first on a duplicate plant to make sure it won't damage them before wholesale spraying. The only problem I've had is that any succulents that have the mealy 'bloom' sometimes lose it for a while. Better that than the critters!
