Z does the same thing if he sees an escaped cricket from the other lizards' cages. He also came from a pet shop as a baby and was fed crickets and broccoli there, so he may have been conditioned into it. The explanation I have heard is that if given no proper food to eat, a starving or malnourished animal will eat whatever it can. The argument would then go that if your ig likes bugs, then you are doing something wrong (not giving it the right ammount of plant protien, whatever). I think conditioning has something to to with it in Z's case. Also, ice cream isn't good for us,but we eat it... But that opens up a whole other debate.