Army ants eschew a fixed nest for a migratory lifestle, moving from place to place while eating any animals too slow to get away. This allows for much more intensive foraging than would be possible with a fixed nest, allowing for very large colonies that sometimes reach more than 15 million individuals. Ultimately the ants' walking speed and prey density must set a limit for the size such a colony could grow to: The ants need to have time to disperse over an area covering enough prey for them to sustain themselves, and then return within a reasonable time, less than half a day.
This makes me wonder what a wasp equivalent of army ants would be like. Typical social wasps fly about 10 km/h, compared to army ants' typical walking speed of about 0.3 km/h. Hence, a hypothetical species of "army wasps" could cover an area (10/0.3)² = 1100 times larger than what army ants can, and catch a correspondingly greater amount of prey. This more than compaensates for the wasps' larger size: A common wasp worker is about 15 mm long, compared to a typical army ant worker's 3 mm, making the wasp roughly 125 times heavier. Ants use about 140 J/km/g, compared to about 45 J/km/g for honey bees, which we can use as a proxy for our army wasps. Hence, it should be possible for an army wasp colony consisting of individuals similar to the common wasp to reach a colony size 1100/125*(140/45) = 30 times larger than that of army ants. That is: a colony size of 10-100 million individuals with a combined mass of 1-10 tons!
Such a large colony size combined with the much higher speed of wasps compared to ants would make this an apex predator capable of hunting not only the small arthropods that make up the majority of the army ant diet, but also large vertebrates like mammals.
This seems like a pretty viable animal to me, so why are there no army wasps? Have I missed a big factor that reduces the maximum viable size of a nomadic eusocial wasp colony by many orders of magnitude? Or is it just an accident of evolution that we don't have to fear a buzzing doom swarm as the top predator in the world?
