Ibrahim Nakha'i says: Every living creature whose blood flows (if it falls into a well), then ablution should not be performed with the water of that well. However, beetle, scorpion, locust, cricket—if they fall into a well, then there is no harm in it (i.e., ablution can be performed with the water of such a well). Shu'bah says: I think he also mentioned the chameleon.