ABUNDANCE, DIVERSITY, AND SPATIAL-DISTRIBUTION OF ANTS (HYMENOPTERA, FORMICIDAE) ON MIXED-GRASS RANGELANDS TREATED WITH DIFLUBENZURON

Abundance of ants on mixed-grass rangelands was not significantly redu ced by aerial applications of Dimilin 2 F, Dimilin 25 W, and Sevin 4-O il. Ant diversity, measured by a probability of interspecific encounte r index, temporarily declined in plots treated with Dimilin 25 W from 13 to 19 d after treatment. However, diversity immediately recovered t he following week and no further declines were observed even at 349-35 6 d after treatment. Twenty species of ants were encountered at the ex perimental site. Lasius neoniger Emery; little black ant, Monomorium m inimum (Buckley); thief ant, Solenopsis molesta (Say); odorous house a nt, Tapinoma sessile (Say); and Formica neogagates Emery were the 5 mo st abundant species at 25.8, 20.1, 9.9, 7.6, and 7.5% of the total num ber of ants encountered, respectively. Spatial distribution of ant spe cies on rangeland appeared to be soil related. Factor analysis of soil parameters (weighted for relative ant abundances) indicated associati ons between ant species and certain combinations of soil properties.