Maybe the issue is that the human capacity for guilt and regret develops later than one's capacity for some of the other emotions, and that one's first experience of something is always the most powerful. But as it stood this was the earliest memory I could identify of feeling guilty about anything, and even as an adult thinking back on letting those ants die was all it took to bring on overwhelming waves of horror.
But in talking to my parents last night I learned I wasn't remembering the facts correctly: the ants had slowly died of natural causes (in fact in looking at the Uncle Milton web site now it even says the ants they ship only live about two months), and furthermore I wasn't even solely responsible for the farm.
I don't have children, I've never owned a pet, and when I lived on my own I was even resistant to having plants. So, since the ants nothing, no matter how small, has ever died of neglect while under my care.
And, now it turns out I didn't kill the ants either.
Hooray for me, I'm a saint.