Silvia Golumbeanu in Nautilus:
Bees are emblems of social complexity. Their honeycombs—intricate lattices dripping with food—house bustling hive members carrying out carefully orchestrated duties like defending against predators and coordinating resource collection. Much of our own success is due to this sort of division of labor. Clearly, in the animal kingdom, it pays to be social: Certain neurons make us resent being alone. You could be forgiven for assuming that complex social organization is the—or at least a—pinnacle of evolution. Yet out of the 20,000 known species of bees, only a few are social. Some bee species have even given up social behaviors, opting for the single life. Why?
For one, as introverts know well, socializing requires lots of energy. Highly complex societies of insects require an elaborate arsenal of chemical and physical signals to direct their communal behavior. Social bees have more highly developed exocrine glands than their solitary cousins, and solitary halictid bees have less sensory hairs on their antennae than their social precursors. Solitary and social halictids also have different odorant systems, which play an important role in social bee communication and recognition. As the environment comes up with new demands, and the genetic makeup of the hive adapts, these features might just stop being worth the investment. For another, being social can be stunting—sometimes bees have to grow up fast to survive. Researchers at Whitman College in Washington found that the region of the newly hatched antisocial orchard bee’s brain responsible for foraging ability is about as developed as the corresponding region in the experienced forager honey bee. Antisociality encourages self-sufficiency. Orchard bees must each fend for themselves, and they emerge into the world knowing how to forage for food. For honey bees, on the other hand, only a portion of the hive has to forage at any given time.
How do solitary species evolve to reap these benefits after having been social?