Odorous House Ants

2011 July 30

On May 28, 2011, our 3-year-old daughter Rosie came into the house after playing in the back yard, trotted up to me, and proudly held out her arms – which were covered with at least a hundred (no exaggeration) of these tiny (2-3 mm long) black ants:

And if you think that getting clear pictures of tiny, scurrying ants is hard, just try it when the ant is on a small scurrying person as well. So anyway, after getting the above picture we brushed them off of her (which she thought was great fun), and I took pictures of some of them on the floor. Which was easier, but not too easy (they were still tiny and scurrying, after all).

Meanwhile, Rosie had dashed back out into the yard, crowing “Get more ants!”, which is how we found out where she was getting them. We have a drainage tile in the back yard, with a plastic storm-drain grating at a low spot. She had lifted up the grating to expose a nest of these ants that were living in the seat where the grating rested. And, since ants have no fear, they were boiling out to defend their nest, and trying to bite her. Without much success, I might add; they were just too tiny to cause any damage, and Rosie just thought that they tickled amusingly. Here’s one trying to bite me, for example:

About the most effective thing they could do was grab hold of a hair and try to pull it out, which all in all wasn’t that effective.

Anyway, these looked like the sort of ants that would commonly turn up in houses. So, I went to Alex Wild’s Guide to the Urban Ants of the Midwestern United States to see if this is one of the ones that he has listed. And sure enough, the very first one on his list looks like a good match: the Odorous House Ant, Tapinoma sessile. This is a widespread North American species, that likes to nest in crevices. There are a lot of crevices in houses, and so they frequently get into houses in some quantity. They are called “odorous” because they have “a distinctive smell” when crushed. Alex calls it a “cheesy” odor, but I didn’t think that narrowed things down that much, seeing as how there are a lot of kinds of cheese. So, of course, I had to crush and sniff one of these ants to check it out for myself. I’d say the cheese in question would have to be one of the Limburger types. Either that, or the inside of a well-aged athletic shoe. Not a pleasant floral bouquet, is what I’m driving at here.

These ants are superficially similar to the Pavement Ants that I posted back in April of 2010, being about the same color and the same size, and similar habits. But, if examined closely, you’ll see that the waist of the pavement ant consists of multiple, kind of bulbous segments while the odorous house ant’s waist is a single, small, thin segment.

Pavement ants
Pavement Ants (left) compared to Odorous House Ant (right). Note the difference in their waists.

Odorous house ants are the ants that are most likely to be found in houses in the Midwest, they seem to be better adapted to the house environment than most other species. They are generalist feeders, willing to eat most of the kinds of foods that people have in the house, but like a lot of ants they particularly like sweets. They’ll also eat other insects if they can get them. They need some moisture to get established in a house, along with suitable crevices to nest in. They are one of the species that can have multiple queens in a nest, so they can get to the point of having a sprawling nest with many thousands of ants given time. If they get into the house, they are best eliminated right away, when they only have one or two queens. I understand that they are easily controlled with the standard ant-baits, although it will only get harder if you wait so long that they have time to get more queens established.

6 Responses
  1. July 30, 2011

    How wonderful that she’s so comfortable around bugs that she finds an armful of ants exciting!

  2. August 3, 2011

    Man, my 14-year-old daughter wouldn’t have been nearly so adventurous! As for photographing the ants running around on the floor in your house, I commend your wife for great patience!


  3. August 3, 2011

    Yes, I appreciate my family’s attitude towards small crawly things very much. They are all as fascinated by them as I am, and are all for helping catch and photograph them. Even after picking up a couple of bee and wasp stings, neither of them shows any particular fear of insects (only a judicious and thoughtful caution around the ones that they know can sting).

    I fully expect that, at some point, we will get a complaint from school that our daughters are terrorizing the other kids with insects.

  4. August 4, 2011

    Hey, man, terror is an internal emotion. Can you help it if the other children were raised in houses filled with nonsensical attitudes towards our six-legged brethren*?

    * – Or would that be … wait for it … aunts?

  5. Dena permalink
    September 12, 2011

    Your photography is fantastic! In the second “ground” picture, I can see the detail of his compound eye. Great Job!

  6. October 8, 2011

    You little one id really brave! I get hysterical whenever a bug or an ant creeps onto me. But I know that ants can bite (and it’s quite painful)…

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