Also called, and miscalled, sugar ants, grease ants, kitchen ants, and house ants.
This is the common ant you may see streaming across your kitchen or bathroom to food
bits, or water.
Buy MaxForce bait stations and put them on the trails you see.
I've used the original MaxForce for an intractable infestation of Pharaoh Ants and given some to several friends -- it works like magic. The company says it also works for Argentine Ants, Crazy Ants, Pavement Ants, Cornfield Ants, Odorous House Ants, Acrobat Ants and Thief Ants. I can't say about all these, but I also used it once for some sort of medium sized red ants coming in from the outside -- it ended them immediately. I've read it also comes in granules -- I've only used the bait stations.
The rest of this article is for you if your ants aren't Genuine Pharaoh Brand, or you're cheap, curious, like to make things complicated or are a glutton for punishment.
Other ants (e.g., thief ants) are often mistaken for pharaoh ants. It's good to be sure you're dealing with pharaoh ants vs some other kind, because the treatment can differ depending on the kind of ant, but a one hour web search failed to turn up a site with pictures that would let you identify them. If your ants aren't pharaoh, you may want to check here.
Pharaoh ants are 1.5 - 2mm (1/16") long and are light yellow to red. It's small size enables it to get into almost anything. Because its food preference ranges from things like syrups, jellies, pastries and grease to toothpaste it has the faculty of appearing all of a sudden in various places in the house. These ants are usually seen trailing along established paths in kitchens and bathrooms.
The pharaoh ant's nature of being scattered about, living in walls and other well protected areas makes them difficult to exterminate.
Control almost has to be with a bait. And it can take months [or days with MaxForce]. From what I've read you shouldn't spray them. Spraying can break one colony into several, making difficult control even more difficult. Spraying their trails may cause them to avoid the bait too.
There is a widely touted homemade bait made from boric acid powder and some foodstuff they like. The common formula goes something like this:
1 level teaspoon boric acid powder mixed well into 5 ounces of one, or some combination, of the following:
Many authorities think mint apple jelly is best. Another mixture you may find recommended is karo syrup mixed with dilute honey.
While researching for this page I saw the following mixture recommended -- three parts honey: two parts peanut butter: one part mint apple jelly: one part egg yolk baby food. Wow! I didn't feed my kids that well.
As I understand it ants look for different things at different times. Sometimes it's protean (fat/grease), sometimes sugar, and occasionally carbohydrate. As I understand it MaxForce contains all three.
When I tried the boric acid method, I put out daubs of each thing I had that I thought might work and waited to see which one they liked best--then I used that. I tested karo syrup, grease, 3 kinds of jelly and peanut butter. In my case they chose peanut butter. I made a bait of about 3-4% boric acid & peanut butter, by volume. Some authorities say 1-2%. A compromise starting point is 2% boric acid. If you see dead ants along their trail to the bait stations your concentration of boric acid is too high. You want them to carry the poison bait back to the nest to feed/poison the queen.
In baiting programs for pharaoh ants it's important to consider their trailing behavior. Baits cannot be placed in just any location and expected to work. Effective bait placement requires trails (to both food and water) be located, and bait stations put on these trails.
You can put the mixture out in jar lids, or fill 1 inch lengths of soda straws and leave these around, or daub it on 2" squares of cardboard, etc. I smeared it liberally on the inside of mason jars creating large "feeding fields" that were protected, to retard evaporation and prevent making a mess. Hundreds, perhaps thousands, of pharaoh ants covered these feeding fields, with dense trails of ants streaming in and out of a nearby wall. They seemed to thrive on it. This went on for 9 months with me changing the concentration of boric acid, until I gave up and bought the Maxforce. I replaced the feeding fields with the Maxforce bait stations and the ants were gone instantly, not to return for 2 years. When they returned the MaxForce worked again just as fast.
NOTE: If you smoke, wash you hands before making the bait or touching the carriers. The tobacco traces can scare off the ants.
I didn't find any really good pharaoh ant-fighter sites but, here are three sites that talk about pharaohs and other ants:
University of Kentucky -- Though it's not tightly focused on food type ants, this is the best page I found on indoor ants.
Ohio States Pharaoh Ant Page (Takes a while for the page to load)