Pheromone baited traps were used to extensively monitor the movement of the Mexican rice borer, Eoreuma loftini (Dyar), through the Texas Rice Belt towards Louisiana from 2000 to 2004. Based on boundary movement, the average rate of spread from 1980 (Weslaco) to 2004 (Chambers County) was 23.2 km/yr. Because frequency of trap monitoring varied between county and year, daily trap counts were determined by interpolation and extrapolation. The annual mean centroid of moths moved 15.3 km in 2001, 5.9 km in 2002, 9.2 km in 2003, and 6.1 km in 2004. From 2000 to 2004, annual mean centroids moved 29.3 km, however 95% CI overlapped across years. The average rate of spread of annual centroids was 4.4 km/yr. The 1.7-fold increase from 2000 to 2004 in ellipse surface area of the 95% C.I. around the centroids indicates an increase in the variability of the covariance of latitude and longitude due to the expansion of the distribution of E. loftini populations.