Do we know of any "species ending bugs"?
From the vantage point of other species, humans might be considered "bugs" in the sense that we are organisms that are causal in the ongoing extinction of numerous species. We're doing a pretty good job of it, so far:


  The included extinctions span numerous families of plants[4] and animals, including mammals, birds, amphibians, reptiles and arthropods. With widespread degradation of highly biodiverse habitats such as coral reefs and rainforests, as well as other areas, the vast majority of these extinctions are thought to be undocumented, as the species are undiscovered at the time of their extinction, or no one has yet discovered their extinction.   The current rate of extinction of species is estimated at 100 to 1,000 times higher than natural background rates.