Ecological Factors Affecting Population Sampling of Desert Tenebrionid Beetles

Population sampling of five species of desert tenebrionid beetles, Eleodes armata, Centrioptera muricata, Centrioptera variolosa, Cryptoglossa verrucosa and Pelecyphorus adversus, was conducted using pitfall traps for 15 months at South Mountain Desert Park, Phoenix, Arizona. Decreases in beetle catch were observed during extreme summer climatic conditions (sustained drought and above-average temperatures) and throughout the colder winter months. The reduced catch was attributed to decreased surface activities and/or increased mortality rates. Increases in number of beetles collected in pitfall traps resulted from general density increases during seasonal periods of population eclosion. Localized elevations in beetle density may have been mediated through the aggregating influences of reproductive chemical pheromones. Beetle associations with desert vegetation reduced their overall population mobility and increased their likelihood of capture in pitfall traps placed near these plants. Some factors such as differential surface illumination due to changing moon phase and remova,l of beetle catch from the sampling area did not significantly affect the number of tenebrionids collected. Density of pitfall traps in a sampling area was critical in determining the number of beetles captured. Comparisons of beetle catches between two spaced-grid sampling areas with different can densities indicated a close relationship between beetle-catch density and pitfall-trap density.