Do fireflies make noise

I just killed a HUGE mound in and around a planter of mine, and after I had poisoned them, I heard a noise I had never heard before. I got my ear as close as I was willing to, and to my amazement, they were scurrying and SCREAMING. I guess if a mound gets large enough and there are thousands of dying ants, this happens. I know I was not "halluci-hearing." Believe it or not...