Significance of the locust
An adult desert locust, it has been estimated, can consume its weight in vegetation daily. A typical swarm can eat as much as 2,500 people can in a single day. And a large swarm—one that stretches for tens of miles and includes millions (or even billions) of hungry locusts—can strip a farmer's field in minutes and leave entire villages with nothing to eat.Certainly, that was the threat posed by this particular makka for the Egyptians who refused to let the Israelites go. But if this is, indeed, a natural phenomenon, how did it contribute to the revelation of G-d? That's the question my grandfather tackles in his commentary on Parshas Bo.
He observes that this makka was unique among the ten. All the others were more overtly miraculous. In contrast, swarms of locust do naturally occur in that part of the world. So the only thing that distinguished this event as one coming from G-d was the the warning that Moshe delivered about it.
This is actually a fundamental point. Some people have put in considerable effort to explaining all the miracles of the makkos and kriyas Yam Suf as natural events. They fail to understand that it's not just a matter of something that could happen within the laws of nature but of the indication that it is planned and executed according to Divine will.