Hello from Mesa, AZ!!
Sooo... We moved into this house this past June and was horrified to see such large (large by this mid-westerners standards) ants, in very, very large numbers on our back patio one morning. That's when the war was waged. I love planet earth, and I respect the Eco system but I have a fearless 2 year old, which kind of changes my perspective on what I will allow in the backyard.
A little bit about our backyard guests. They don't like the heat. They are most active at dusk and dawn. They spread around their colony hole then have deliberate lines to food sources. Basically, they act like every other ant I've ever encountered. However, they have a very strong exoskelaton, and need to be repeatedly stepped on before being crushed. Apparently, the lizards in our yard.don't eat them, since they have such large numbers.
To date we've had an exterminator spray multiple times, landscaper used fire ant pellets, and this evening, out of frustration, I took a pick axe, lighter fluid, newspaper and a lighter to the colony. I wasn't sure if they stung before lighting them on fire, and quickly learned that they do sting/bite and.... it really hurts; which is upsetting because I don't want my curious toddler to have to endure this pain.
So... As I iced my ankle, while watching SpongeBob, and supressed the helpless feeling in the pit of my stomach, I found your site. And how WONDERFUL of a site it is!! After combing through it, I couldn't find my critters. So, here is my plea. What are these large black ants and how do I get them to move to my neighbors yard (or, how do I kill them?). My apologies for not having better pictures, it was the best I could do.
We are sorry to hear you are having a problem with the ants in your yard. Moving from the midwest to the deserts of Arizona means you will have to adjust to your new neighbors and this includes the ants. On a positive note, many of those new neighbors (including the ants) are really amazing! In fact, Arizona has over 300 species of ants. Antweb has a page dedicated to the ants of Arizona: http://www.antweb.org/arizona.jsp
The ants you have in your yard are harvester ants in the genus Pogonomyrmex (probably Pogonomyrmex rugosus). These ants are primary seed harvesters, although they will also collect dead insects and other foods. You can read more about this species and see photos here. You can also find distribution maps for the North American species of Pogonomyrmex here.
Although these ants do have a painful sting when disturbed they are not likely to enter your home. I know that you are concerned about your child, but I would talk to other parents in the area to see how they have learned to live with these ants. Harvester ants are a common and important part of the desert ecosystem, so trying to find a way to coexist with them will be easier in the long run than trying to get rid of them. If you are determined to get rid of the harvester ants in your yard read here and here.
I hope you find a way to enjoy these beautiful ants (see close up photo here)!
Corrie Moreau & the AntAsk Team