Bullet Ant (paraponera clavata) - This ant delivers what is widely acknowledged to be the most painful insect sting in the world. It causes severe pain and uncontrollable spasms for up to 24 hours. Siquerres, Costa Rica. paraponera clavata - This ant delivers what is widely acknowledged to be the most painful insect sting in the world. It causes severe pain and uncontrollable spasms for up to 24 hours and is so named because the pain is said to be similar to being shot. Siquirres, Costa Rica.