Ants in your house or yard: March 2012 Archives


Hello,

I have an old half buried patio next to my house that I plan to un-bury and relay the bricks. There seems to be a large ant colony that lives within these old bricks though. Last year, it was there as well, and in observing the ants, I noticed there were more than one species present (not living peacefully but rather keeping one another in check, perhaps?) Obviously I don't want to have a patio where there are several ants, but I was wondering if there is a way to get the ants to move the colony without getting rid of them? The yard seems to have a good level of checks and balance of living things, and I don't want to disturb that balance.

Any help is much appreciated.

Thank you
Jackie

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Hi Jackie,

The ants visible in your pictures are probably Formica subsericea. These ants sometimes host so-called slave-making ants, caring for their dominant partners without having a queen of their own. It is possible that the Formica subsericea ants you have seen are living as slaves of another species, explaining the presence of other types of ants. If this was the case they would act peacefully towards each other as they are members of the same colony.

Moving a colony without destroying it is very difficult. However, many ants regularly relocate their nests on their own, and it turns out that this behavior has been previously studied in Formica subsericea (Smallwood 1982 - full citation below). According to Smallwood (1982), Formica subsericea change nest sites about every 90 days. So if you wait long enough, they may leave on their own, though they could be replaced by yet another colony. Ho¨lldobler and Wilson have a section on ant nest relocation on page 171 of their 1990 book, "The Ants". They discuss a number of factors that are known to motivate some ants to relocate their nests including mechanical nest disturbance, flooding, competition, and predation. I doubt you want to prey on these ants but, given enough disturbance, they may choose to leave on their own. Digging up your old patio may be all the motivation the ants need to leave.

Thanks for your question and good luck with your patio,
Ben Rubin, James Trager, & the AntAsk Team

Smallwood J (1982) Nest relocation in ants. Insectes Sociaux 29:138-147.

I live in Santa Fe, NM, and am trying to cope with an ant infestation. I've attached photos including a millimeter ruler so you can see what they look like. They go after food mostly. They loved the inside of the dishwasher when there were dirty dishes there - until I put ant powder under the dishwasher behind the toe kick plate. We've been fighting them for months. We started with ant traps, but they don't seem very interested in them any more. Ant powder is very effective, but as we have a little dog we must be very careful where we use it. We recently found a nest behind a radiant heating panel at the bottom of a paneled wall (indoors). I'm pretty sure there are multiple colonies by now. Any suggestions will be most welcome.

-Steve

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Hi Steve,

These ants are Tapinoma sessile, ID courtesy of Dr. James Trager. Commonly known as "odorous house ants" or simply "stink ants", this species is widespread across North America and frequently invades homes and other buildings for easy access to both food and favorable nesting sites. They actively colonize near heat sources or in insulation for effective brood-rearing, which explains their affinity for electrical appliances like dishwashers and radiant heat panels in your own home. They are largely harmless as house pests go, but if they become too much of a nuisance, there are a number of comprehensive steps to follow beyond laying traps and applying commercial ant killers. The following post addresses domestic ant control measures in fairly exhaustive detail, but you can also refer to other tips for containing ant infestations here and here. If you want to learn more about this species and see some stunning up-close photographs, check out this post by insect blogger and fellow myrmecologist Alex Wild.

Hope this helps,

Alexandra Westrich & the AntAsk Team

I have lived in my present house, in Cupertino, CA (a suburb of San Jose) for 20 years. For the first ten of that, ants were very invasive (into the house), and hard to control. A scientist at Stanford University, D.M. Gordon, published an article in the local paper, saying that the ants in the area were argentine ants. However, for the last couple of years, there are almost no ants at all---not only in my yard, but in the whole neighborhood. I have had a couple of instances of ants showing up in my "no ant" zone (about 3 feet around the walls of my house), but they were much smaller than the argentine ants, and when I invited them to leave, using black pepper by the entryways and on any apparent nests in that zone, they politely did. Leave. When I look around the yard, and the neighborhood, for ants, usually I don't see any. This seems like a bad thing to me, I thought ants were supposed to be very good for the soil. Any thoughts?

- Sally
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Dear Sally,

Thank you for contacting AntBlog with your observations about Argentine ants in your neighborhood. We contacted Argentine ant expert Dr. Neil Tsutsui and here is what he said:

"The ants that you used to have in your yard were probably introduced Argentine ants (Linepithema humile). These are, by far, the most common ants in the Bay Area. A few native species of ants, such as the odorous house ant (Tapinoma sessile) pop up here and there, but they are generally less abundant and less widespread than Argentine ants in urban coastal California.

I've heard a few anecdotal stories of Argentine ant populations crashing (and disappearing) in locations where they were formerly quite abundant - both here in California and in other parts of their introduced range (like in New Zealand). Nobody really knows the cause, but it's an active area of research.

Overall, I would say that the absence of Argentine ants in your neighborhood is a good thing - less of a pest problem for homeowners, and their absence may present an opportunity for some of the native species to become re-established."

Best wishes,
Neil Tsutsui (Guest Expert), Corrie Moreau, & the AntAsk Team

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