I think every kid in the midwest pulled a leg off a daddy long legs[1] at some point. They would keep moving afterwards, and to a kid this was fascinating (and reinforced the belief they were not like animals and could not feel pain.)
Regardless, now that I'm older I think most living things have a purpose and try not to bother anything that doesn't bother me, but yes, reading this I feel guilty :(
I never pulled legs off arthropods, nor did I ever use magnifying glasses to burn them. I did witness other children doing these things, and it always upset me intensely.
I'm probably an outlier. My mother tells me that from the time I could walk I captured bugs in the house and carried them outside to prevent them being killed.
I've continued the habit of rescuing animals from bad situations into adulthood and rapidly-oncoming old age. Once I caught a hummingbird in an Apple building in Cupertino and let it go outside. It was a beautiful iridescent green and so light that I couldn't feel its weight in my hand.
You’re not alone. I never tortured any insects or animals as a child and it weirds me the fuck out that that is apparently considered normal behavior. I haven’t seen signs of this in my own kids but then again I’ve taught them explicitly that harming sentient beings is wrong.
I think it's possible that we might be the weird ones. In the environment that our distant ancestors inhabited, squeamishness about harming animals might have been a significant disadvantage.
Or maybe not. Joseph Campbell claimed that a common feature of tribal mythology is ceremonial apologies and restitutions to animal spirits to make restitution for the need to kill them.
I think it all depends on the adults in your life. Maybe if we'd had a leader who said don't do that instead of "well they can't feel pain and they're pests" things would have gone differently.
