蚍蜉撼大树pí fú hàn dà shù

撼：摇动。蚂蚁想摇动大树。比喻不自量力。

例蚍蜉撼大树，可笑不自量。——唐·韩愈《昌黎先生集》

英an ant trying to shake a big tree—ridiculously overrating one's own strength; futile effort;

亦作“蚍蜉撼树”