Jackie, i think what you're call locust is a cicada (sp?)-- and they make clicking noises, and the faster they click, the hotter it is --(and they are commonly called locust here, too)

the times article pointed out that when grasshoppers swarm, they become locust.. (as in a plague of locust)

there was a NOVA (PBS science show) about them one year.

in times of drought or famine, grasshoppers, (usually pretty solitary insects) keep meeting each other.. this interaction actualy causes hormomal changes, and the insect that is in normal times a loner, now begins to swarm.. and as it begins to swarm, each insect gives of a pheramone (a scent hormone) that increases the chances of other grasshoppers joining the swarm. at the same time, the hormone actually changes the the insect.. (How?--i dunno. i remember seeing side by side ilustrations.. but i don't remember the details... but they did look different.)

one change was, digestive.. instead of just eating their normal food, a swarm will eat anything.. the times article said that house wife's would put heavy woolen blankets on there vegetable gardens to protect them.. and the swarm would first eat the blanket, and then, finish off the garden for dessert! not normal eating habits for grasshoppers.