“Anna Dornhaus, a University of Arizona researcher, painted ants different colors to study them. Great differences were found in the speed of ants’ work, and about 50 percent were found to do no work.” [link]

And you thought I was referring to humans? :) Looks like its about the same case with humans too.

Perhaps the division of labor — which the economist Adam Smith linked to human achievement — may not be the key to ant success. Possibly, Dr. Dornhaus said, “the lazing ants are resting, or are waiting in reserve in case something goes wrong.” Or the laggards may be cooking up some biochemical nest protection. (All ant species manufacture a fungicide to stave off mold in their nests.) Or, she said, “It’s possible they aren’t doing anything at all.”