Okay, this is near the end when Cassie made the deal with the yeerk about staying a caterpillar. They wanted to talk to Cassie when she was a Chrysalis, but they 'couldn't' because she could not hear as a Caterpillar or a Chrysalis... Yet, what about thought speak? Tobias and Ax could have easily spoke to her, and since she was in a morph she could have thought-spoken,too!