A five year study, in the desert grassland of New Mexico, sampled arthropods living in the canopies of two woody shrub species (Gutierrezia sarothrae and Prosopis glandulosa) and perennial grasses with associated herbaceous species on 18 plots. Mesquite shrubs were removed from nine plots, six plots were grazed by yearling cattle in August and six plots were grazed in February for the last three years of the five year study. Arthropod species richness ranged between 154 and 353 on grasses, from 120 to 266 on G. sarothrae and from 69 to 116 on P. glandulosa. There was a significant relationship between the number of families of insects on grass species and G. sarothrae and the growing season rainfall; although, species richness was not a function of growing season rainfall on any of the plants. There were more species rich families shared by grasses and G. sarothrae than by mesquite. Removal of a dominant shrub (mesquite) from the system did not have the anticipated result of lowering species richness. However, summer grazing of plots, in several cases, lowered richness in comparison to plots that were ungrazed or winter-grazed.
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