What are these ants in my home? Carissa, Texas, USA

Greetings AntAsk!

I must say, having Googled my way to your site while searching for possible identification of the new ants that have found their way in, I found myself going through many pages of archives and forgetting why I started reading your blog in the first place. But I do have an identification issue I'd like your two cents on, if you could. Picture attached (after trying two different cameras and about 30 minutes of fiddling with settings to finally get a shot that wasn't just a massive blur).

I am in northeast Texas, and early last week we got hit by the mother of spring rains including damaging hail and some tornadoes. I also had our quarterly pest control visit 5 days ago. I think these guys got washed out or relocated by the weather, then further disrupted by the Orkin man. I noticed ants in our kitchen two days ago - though NOT by the food or the pets' water bowl not four feet away, just crawling along the baseboard by the backdoor. One quick Terro treatment and they were gone. This morning I found the same kind of ants on my bedroom windowsill.

This time, though, they weren't marching anywhere. There are three relatively gigantic (half-dollar-sized) collections of them clinging to the wood and the wall along the corner of the windowsill and only a couple moving in through what I can only assume is a microscopic crack in the window. I have another Terro treatment down and have a call in to the Orkin man for a re-visit, but I kind of want to know what you think.

My Google-assisted guess is that they're Argentine ants potentially out recolonizing/mating, but I'm very much a layman when it comes to mermecology, so that's just a stab in the dark from a curious mind. Two questions come to mind right now: 1) what are they, and 2) how much weatherproofing am I looking forward to in order to shore up any cracks in windows/doors/baseboards/etc.?

Thanks in advance!

Dallas, TX


Dear Carissa,

Thanks for the question. Unfortunately, some of these likely subjects are difficult to tell apart with out a microscope. There's a good chance they're the common Tapinoma sessile. One of our other experts, James Trager, writes: "I'd be willing to make a small bet they're Tapinoma sessile. Terro baits keep them at bay in my house (at my wife's insistence), without, I am glad to say, harming the numerous colonies around the yard that do not enter the house."

It is difficult to rule out Linepithema humile, however. In general, T. sessile is more likely to be spotted inside a house. In the field, they actually can be distinguished by their odor if you pick them up and schmush them a little between your fingers, but this takes practice, and some familiarity with both. The difference in odor is difficult to describe (T. sessile has been described as being somewhere between 'coconut' and 'citronella').

Regardless, the fact that they are attracted to terro baits is encouraging. No matter what the species, the trick is that one treatment is never enough. At most, you generally take out 80-90% of the ants, so they'll quickly bounce back if you don't keep applying. For the cost conscious, the terro-bait recipe can be pretty much replicated with sugar, water, and Borax by following these instructions (click here).

Weatherproofing would probably help, but personally, I'd wait a little while to see how the bait was working.

Hope this helps!
Jesse Czekanski-Moir & the AntAsk Team

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