Ant identification: 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

At a trip today (July 10th) to Boise's MK Nature Center (operated by Fish and Game) our group of preschoolers found a pile of ants. I told them I wasn't sure what they were doing, but I would take a picture and ask someone. So, I found you online! These are just small black pavement ants, I believe. Any insight on what they are up to?

Thank you for your time,


Dear Tricia,

Thank you for sending in the photo of the ants your preschoolers noticed on your recent nature trip. Great find!

The ants are in fact pavement ants in the genus Tetramorium. Although this is a common ant found in urban environments, it can also be found in more natural habitats. Along with the pavement ant, there are likely dozens of other ant species in that same nature reserve, so keep your eyes open the next time you visit the reserve. Close by in the state of Utah over 150 species of ants are known (see the Ants of Utah on

You can read more about pavement ants here in a previous AntBlog post.

Thank you,
Corrie Moreau & the AntAsk Team

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