The lizard usually depicts your most fundamental and inbuilt responses, such as the fight or flight response, drive to procreate, territorial feelings, ritual behaviour. These are part of your primitive brain functions, and are very necessary. Because of this, the lizard and more so the snake, can represent the very process of life in you. This life activity flows through your functions and expresses as what you experience. So emotions for instance, are a particular expression of this life process. But emotions can be crippling when they are all to do with fear, guilt and self-incrimination. Therefore the lizard or snake can be shown as deadly, poisonous, and it then needs to be led in another direction. i.e. your emotions and anxieties, those basic responses, need re-channelling.