We're all biased...if I had to choose between a family member dying and a stranger I would choose the stranger. I don't believe my family members lives are worth more, but I am certainly biased towards protecting them. If I had to choose between a human and a cow...sorry cow. I'm biased towards humans. Mammal vs insect? I'm on team mammal. That's a reflection of our bias/subjective valuing of lives...and I think that's forgivable, as long as we recognize it as bias and not some objective hierarchy of suffering. In reality we don't have to choose to kill either one animal or another, though. The choice is to kill or not to kill. And I think that choice should be guided by the same principles for any member of the animal kingdom...I'm just not sure what those principles are, precisely.