Ants in your house or yard: July 2012 Archives

I just moved to Costa Rica for the next 5 or so months to a beautiful beach house. The bugs are hardly noticeable during the day, but when the lights go out...they come out to play. Since it is such an open home (literally doesn't full close) I get a bit creeped out at night.

Specifically there are these very large black ants; much larger than anything back home. After some online reading it seems that they might be Bullet Ants. Reading that they only come out when I sleep and have very painful bites...a bit unnerving. I don't mind running into them outside, but the prospect of meeting them in my sleep is really giving me the heeby-jeebies.

There is no food around where they are entering, I can't really find the entry point to block it, and I cleaned the area to try to remove any trails left behind. What can I do to create an ant free sanctuary in my bedroom at night? Being in a small surf town in Costa Rica, I'm not sure what products I can or cannot get my hands on...

Also, this spurred another question. After manually killing a bunch in my room the good-ole-fashioned 'shoe' way I began to wonder, will ants ever leave an area after seeing too many of their own dead? Or do they just blow on by without a care?




Dear Benjamin,

Without pictures it is hard to tell exactly what species of ants are raiding your bedroom at night, however, there are a few clues which provide enough evidence to give an educated guess. First, from the sounds of their behavior, it is unlikely that these marauders are Bullet Ants. For most people, a single bullet ant sting will incapacitate them for a day, and several in a night time might demand a trip to the hospital.

On the other hand, the western coast of Costa Rica is known for a black subspecies of army ant, Eciton burchellii parvispinum, that tends to frequently raid manmade structures in the day, evening, and night. They are much larger than most North American ants, come in great numbers, and also have very potent stings. Most army ants have a predilection for wasp larvae, and due to the high incidence of wasp nests on the eves of dorms and houses, the army ants will continue to return to clear them out. On the bright side, army ants are nomadic so they probably won't be around for long, but it could be as long as 3 weeks before they move their nest site. The best solution would probably be to get a netting for your bed so you can avoid contact and sleep in peace. They're cheap and you can rest easy as the army ants clean your beach house for you!

In response to your other questions, the answer depends on the species! Often, ants will release an alarm pheromone to communicate to other members of the colony there is a threat. For some species--even some army ants--this will cause the rest of the colony to avoid that area. However, if these army ants are the species I'm thinking of, they have colonies of with millions of workers, and make their living by overwhelming and consuming their prey. Often killing a few workers of an Eciton burchellii colony will just rile the rest of the workers up and incite further aggression.

Hopefully the bed-net solution works for you!

Max Winston & the AntAsk Team


We have a thin crack in the concrete at our garage door. Tiny ants keep bringing up small particles of something. At first I thought they were in the wood door frame as the residue was piled along it. After taking trim off there were no ants.

Have placed terro at the action site but, they keep on coming. Have sprayed, it lasts a few hours and they are again active. Blowing forced air from an air compressor brings them up. Kill them with spray, squirt it in crack and the ants return next day.

The crack is too small to really get anything in it. What next??

Thanks, Fred, Ovid NY

Dear Fred,

Sorry to hear you are having problems with ants in your garage. Although ants are an important part of the balance of the natural world, unfortunately they can also become pests in our homes. Using commercial sprays is usually ineffective, since they only kill the few workers or foragers you see. The rest of the nest, including the queen, is usually far away (deep underground or inside wood or a tree), safe from the fumes of the bug spray. To truly eliminate the entire colony, you must find a way to kill the queen.

In previous posts on AntBlog (click here, here, here, here), we have outlined some general strategies for getting rid of ants including using commercially available poisons like Borax.

Best of luck,
Corrie Moreau & the AntAsk Team

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