If it helps, think of the Utricating hairs as miniature porcupine quills, when a New World Tarantula is disturbed, it turns it’s abdomen towards the “threat” and rapidly rubs it’s abdomen with it’s back legs, sending off a cloud of hairs (often referred to as “kicking hairs”)
generally, tarantulas have 3 levels of threat response before they’re forced to bite…
1; RUN AWAY!!!, a tarantula would prefer to hide from the threat if at all possible
2; Threat Display; it will rear up on it’s back legs, often baring it’s fangs and raising it’s front legs and pedipalps (food handling legs), basically saying “GRRR!, LOOK HOW BIG AND MEAN I AM!!! GO AWAY!!!”
3; Kicking hairs
if these three threat levels don’t work, and the spider sees no other choice, it may bite, even then, it’ll be a 50/50 chance of whether the bite is “dry” (no venom injected) or a true envenomation, the spider would prefer to use it’s venom for it’s intended purpose (feeding) rather than use it for defense…
as far as the OP’s “prank”, assuming we’re not being “wooshed” here, i also would like to voice my displeasure at the “prank”, it’s not funny, and will be needlessly cruel to the spiders, then again, i like my Arachnid freinds (with the exception of ticks, those you can kill), and i’ve been known to release spiders outside when i find one trapped in a tub or sink or shower or something, these all have been hand-captured, and i’ve never been bitten, but then again, i recognize Arachnid threat displays and will adjust my responses accordingly
if we’re not being wooshed, please reconsider this cruel prank