Fire ant workers are only about 1/16 inch to 1/4 inch long and have reddish brown bodies and black abdomens. Variation in size is one distinguishing characteristic of imported fire ants. Workers of many other ant species are uniform in size. If the ants in your house are different sizes, and are very aggressive, they may well be imported fire ants. Your Extension agent can help with ant identification. For information about home-invading ants other than fire ants see FAQ #3318, "I have small black ants about 1/8 inch in length in my kitchen and bathroom. What can I do to get rid of them?" and FAQ #831, "What are some options for controlling imported fire ants inside my house?"