Evolutionarily speaking, insects pioneered social structures [source: Misof et al.]. Today, the 2 percent of known species that have this trait make up roughly four-fifths of the planet's insect biomass [source: Johnson and Carey]. What's more, taken together, their ecological impact can outclass just about any other animal. South American leafcutter ants, for example, chow down on more plant life than all plant-eating mammals on that continent combined [source: Meyer].
True social, or eusocial, species share four key traits. Their members occupy a shared nest site; team up to raise young; split labor between sterile (or less fecund) workers and reproducers; and live side by side with overlapping generations. Although many insect species have one, two or even three of these traits, only a few have them all. They include all termites, all ants, 600 species of bees (family Apidae) and 700 species of wasps (family Vespidae) [source: Meyer].
Of course, social structures carry risk. Infectious diseases and specialized parasites can wreak more havoc, and members must vie with one another for resources. But weighed against a large, expert and robust workforce for building, food gathering and defense, the rewards of a large social populace become clear.