How do you humanely kill arthropods?

Answer 1

The most humane way is freezing them. A cold arthropod will be slowly knocked out and won't feel a thing of death, but if you don't freeze it long enough and it doesn't die, it will revive again! Scorpions are notorious for surviving being frozen in a solid block of ice and they're not the only ones! They won't be angry, obviously, so don't be scared by the idea.

Another way is just swatting it utterly, as fast as you can. Small insects and Spiders shouldn't be much of a problem, but don't try this with crabs or tarantulas, of course. You could also suffocate them with carbon dioxide, perhaps fill the terrarium with it if this concerns a pet.

And of course, if possible, just put the beasties outside. No need to kill anything if not completely nessecary. ^^