Ants Relocating

My work is often interrupted by the activities of some animal behaving in what I consider a strange manner. In this case, my trip into the barn in search of a tool was put on hold when I spotted an ant pupa and its accompanying workers. The large size and presence of wing pads indicated the pupa to be that of a queen ant. I find similar pupae regularly every year, so the encounter wasn’t unusual. What puzzled me was the reason for its being out in the open on my barn floor.

As I opened the door further, it became apparent that the pupa was not alone. Pupae were scattered about the floor in an area several feet wide.

The ants are a species of Crematogaster, a fairly common ant in most areas. They are known by their heart shaped abdomen, called a gaster, which is capable of delivering an irritating liquid from its tiny sting. These individuals are in their classic defense pose with jaws agape and sting aimed up.

These ants are clearly caring for the pupae. They were certainly quick to attack my little finger when it brushed the floor while I took this shot. The darkening of some of the pupae indicates that adults are nearly ready to emerge. A few winged males are already in evidence. But the question of why they’re scattered across the floor remains, at least until a rain of pupae falls on my head.

A look toward the ceiling answers my question. Crematogaster ants are known for carrying their pupae aloft prior to the emergence of adults. It’s not uncommon to find pupae in the mailbox or one of the bird boxes. In this case it seems that the ants are trying to squeeze the pupae into a tight spot beneath the boards of my barn ceiling. As additional ants pile on to the heap, the mass becomes unstable and clumps of ants and pupae fall to the barn floor.

The whole operation reminds me of a mountaineering expedition. The ants scale the vertical face with temporary encampments along the way.

At the bottom of the wall is the base camp. Pupae are piled in readiness for the trip up. The pupae from the floor were eventually moved into this position. While I was watching, I witnessed two ant avalanches. Those are tough little creatures to withstand that fall without injury. I wonder how many times they were carried aloft before their position was secured.

It seemed to take a standard squad of five workers to transport a queen pupa up the wall. In typical Three Stooges fashion, I saw a couple of instances where a worker actually stood on the pupa while pulling. The rest of the ants continued carrying their companion along with the pupa. Could there be such a thing as a lazy ant? When I came back a few hours later the floor and staging area were clear. Sometime in the next few days I’ll probably be able to witness the mating swarm depart.