Queen Ant – Formica

2007 December 22

These ants are all over our yard. They tend to live in pretty substantial nests under objects, and they sent queens like this one out on mating flights in the middle of July, when I caught her:


You might notice that she only has one wing. The other had been torn off, probably because she’d finished her mating flight and was looking for a good place to make a nest. The reason the other one looks a bit funny, is I had tried to stick her down with a drop of honey so that I could get a good picture of her underside:


including a zoom in on the underside of her head:


I tried to get a picture of her face by holding her between my fingers, but she did not approve:


so I ended up refrigerating her so that I could get a side view, and a close-up of the head showing, among other things, the ball-and-socket joint at the base of the antenna:



So, based on the coloration; the shape of the head, eyes, and mandibles; and the nature of the nests I’m going to say that it is probably an ant in the genus Formica. This genus has a number of species that have a red head and thorax and a black abdomen, and once again it takes an expert to narrow it down to the species level.

We probably actually have several different Formica species in our yard, because some of them build these massive mound nests, while others build little nests under rocks and pieces of wood. Something we have seen them do a couple of times is carry out “slave raids”: the most extreme one was where we noticed a continuous stream of ants going across the driveway, and coming back with ant cocoons in their mandibles. We tracked down the ends of the ant stream, and found the hill being raided under some mulch around a young tree in the back yard. Following the raiders back to their nest, we found them under our propane tank in the front yard, a good 200 feet away! And there were enough ants involved in the raid that there was at least one ant every couple of inches along the whole route. As near as we could tell, both the raiders and the raidees were species of Formica, although probably not the same species. The idea of these slave raids is that, once the cocoons are hauled home by the raiders, the adult ants will emerge from them and behave as if they were part of the raiders’ nest all along. The advantage of this for the raiders is that they did not have to invest eggs, food, or time in producing these workers, who are now all raring to go and ready to support the nest of their masters.

As a result of the slave raiding, the hills of these ants are very diverse. One that Sam and I dug into over the summer had large red-and-black ants with substantial heads and mandibles (“major workers”, or “soldiers”), smaller red-and-black ants (“minor workers”), and even some black and brown ants that had evidently been hauled into the nest as slaves. The soldiers can give a somewhat painful pinch when they bite, but evidently can’t break the skin. Which is a good thing, because if they did break the skin, they could then spray their formic acid into the wound, which I’m sure would be quite painful.

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