Researchers studied eight ant colonies comprised of 150 ants each, and found that in some colonies as many as 30% of the ants did not partake in egg cleaning or larval care. However, the inactive ants were there to take the place of others that grew fatigued, allowing the colony to operate smoothly.
"Each ant has its own threshold for rising to the occasion and starting work. Simulations showed that a colony comprised entirely of active ants was less likely to be able to sustain itself than one with ants of varying degrees of motivation," said one of the doctors involved with the study.