What or who are the Vuvv in the novel, Landscape With Invisible Hand?

The Vuvv are the alien beings who invade and take over Earth, and they symbolize the worst fears humans have regarding the ruthlessness of an alien race. In an interesting choice, the author describes the vuvv as being short, broad, and walking on all fours, resembling a coffee table. The individuals are not referred to by gender, but are called “it” regardless of the name (such as Shirley).