Eciton Matriarchy

Dr. Theodore Christian Schneirla of the New York Museum of Natural History has one absorbing interest in life. An animal psychologist of renown, he would rather study the army ant than any insect he knows. Last week he was back in Manhattan from the Canal Zone with new lore about the most predatory of ants and its life in a society of fierce complexity.

Army ants march through tropical forests in narrow, hurrying columns or large sweeping masses. Some are going out to battle, others returning with prey, i.e., food for the central colony. Their captures are mostly the young of other insects, but few creatures, large or small, dare brave the ferocious army ant in his full military array.

On Barro Colorado Island in Gatun Lake, Dr. Schneirla followed the columns of army ants to their strongholds, then studied the biological mechanism which governs their lives.

In colonies of the species Eciton hamatum, he found 65,000 citizens or more. Most of them were workers, virgin females up to four-tenths of an inch long, which are denied the work of reproduction by the laws of the tribe. In the colony there are one completely developed female, the queen, two-thirds of an inch long, and a few harried winged males, often transients from other colonies. These the ferocious virgins coddle, and hold in captivity. In time of hunger they may also devour them.

For about 17 days in a regular cycle, the colony moves its bivouac every night. Toward dusk one of the raiding columns loses its martial excitement, slows its pace. Then the raiders fall into a steady, plodding lockstep. At the far end of the column, up to 200 yards long, they clot together in a tight, solid mass. The news of the move spreads back to the previous bivouac. As raiders come in from forays in other directions, they turn and follow the plodding column.

Stay-at-home workers pick up the squirming white larvae, over 30,000 of them, and carry them slowly over the same path. The winged males straggle along, licked and caressed by the workers, but bitten fiercely if they try to fly away. The queen comes too, guarded by a crowding escort of fanatical worshipers. She plunges into the mass of her subjects at the new bivouac and disappears. The colony has moved.

Royal Confinement. This happens every night until the larvae are enclosed in cocoons to change into motionless pupae. Deprived of the stimulation which they get from, the larvae's squirmings, the workers lose their restlessness. The whole colony marches into a hollow log. After a few days of this seclusion, the queen is gravid. Her abdomen swells enormously, and she lays some 30,000 eggs, which hatch into tender white larvae. When both larvae and "callow" ants are ready to travel, the colony becomes nomadic again.

How and when does a queen begin her reproductive life? Dr. Schneirla is not sure, but he has a theory. While the queen is in a bivouac, she is always surrounded by a dense mass of workers, which struggle wildly to lick some substance exuded by her body. The males, no matter how eager, cannot get anywhere near her.

But when the queen is on the march from bivouac to bivouac, she is relatively unguarded. Then, thinks Dr. Schneirla, the hitherto frustrated males may get their chance.

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