Abstract: Following the first occurrence of fire ant, this study was conducted in order to identification of responsible species, determination of local dispersion and study on some biological and ecological features in Sistan and Balouchistan province, southeast Iran from 2003 to 2004. The collected samples are preserved in 70% alcohol and identified. All fire ant samples which collected from various areas were identified as P. sannaarensis, (Hym.: Formicidae). Dispersion area is occurred in the Iranshahr, Sarbaz and Nikshahr districts. The ability for colony making in fertilized workers was surveyed at the field condition using 20 plastic open cylinders at alfalfa farms. The winged ants appear in the early spring and early autumn. The casting system is not observed in the populations of any studied colonies. The threshold of vital temperature is ranged between 0 to 55°C. Their complicated underground gallery is about 1 m in deep with small barely opening. Their colonies were built in humid microclimates at the parks and loans, near irrigation channels, below man-made concrete surfaces at shadow of trees and alfalfa farms and so on. Domestic and global expansion of P. sannaarensis may boost following developing of transportation nets to studied area as well as increase in rainfall.