A million ruby-throated hummingbirds will consume much more food than one African Elephant, even though both have about the same biomass (3,000kg, or 3.3 US tons). Thus, ants, as a group, may actually consume more resources per year than antarctic krill, even though both may have roughly the same biomass, because ants tend to be smaller, and live in warmer environments. Although there may be about 10-15 times the biomass of termites than cows in the world, studies have suggested that termites might produce almost 30,000 times as much methane per year because of their faster metabolism.
http://www.antweb.org/antblog/2010/10/do-ants-really-have-the-largest-biomass-of-all-species-on-earth-laurie-usa.html