I accidentally opened up this nest of Pseudmymex ants in Argentina while trying to see where a worker carrying a caterpillar had got to. This promoted a flurry of activity as workers grabbed brood to carry to safety. The pale white ants are, in fact, immobile pupae (the equivalent of a cocoon or chrysalis in a butterfly) getting ready for their final molting into active adults. You can see one dark pupa that is nearly ready to eclose. The small white objects are eggs, but no larvae appear to be present in this portion of the ant nest. Ant larvae look a bit like small grubs or maggots.
Pseudomyrmex are occasionally called twig ants. The genus name, Pseudomyrmex, means “false ant,” because the original descriptor of this genus thought he had discovered an ant-like wasp. Pseudomyrmex are very interesting ants. Fairly large, if slender-bodied, manyPseudmyrmex species live in relatively small colonies (often only 30 to 80 individuals, compared to the hundreds of thousands seen in species like fire ants). Individual workers forage alone, able to take down prey and return it to the nest without assistance. Personally, I call these ants tiger ants–fierce, sleek, and deadly solo hunters.
These ants also include the acacia ants, and other tree symbionts, whose colony sizes can number in the millions. In these mutualistic systems the tree provides the ants with specialized food and nesting space and the ants fiercely defend the trees.