How the Earth Got Fixed

On Tes’russ, there is but one sentient life form, the uss. There are, however a vast number of diverse organisms that form a complex, interdependent ecological matrix. One of those organisms is the creeky spider. It’s not a spider in the Earth sense of the species, but it looks enough like a small yellow, white and orange spider that humans mistook it for one when they first came across it. It makes a creeky sound when it walks, thus its name. Nobody on Earth paid enough attention to realize that the creeky spider was spearheading an alien invasion.