Activities of Certain Species of Eleodes in Relation to Season, Temperature, and Time of Day at Joshua Tree National Monument (Coleoptera: Tenebrionidae)

Abstract

Members of the genus Eleodes at Joshua Tree National Monument live under daily and seasonal environmental extremes. Overt activity is consonant with these conditions. The data from five different laboratory and fiield procedures indicate that surface activities generally occur when the ambient temperatures are between 12-280C. As ambient temperature increases, Eleodes spp. select relatively cooler microhabitats; as ambient temperature decreases, Eleodes spp. select relatively warmer microhabitats. In the spring the insects are mostly diurnal; in the summer they are usually crepuscular or nocturnal; most beetles hibernate during the winter. Much of the activity period is spent foraging on small green herbs; however, individuals will eat almost any plant and sometimes animal material that they encounter. Inactive periods are spent in sheltered microhabitats such as rodent holes and crevices between rocks. Beetles of the genus Eleodes Eschsholtz are members of one of the most conspicuous groups of desert animals. They are large black ter- restrial insects, usually having moderately long legs. Eleodes spp. are of considerable interest because they principally live in North Amer- ican deserts (McColloch, 1918) and seemingly are exposed to intense solar radiation, high temperatures and low humidity (Buxton, 1924; Jaeger, 1950). Investigators are beginning to look at the adaptations for desert existence found within this genus. Tanner and Packham (1965) reported on population dynamics at the Nevada atomic test site. Ahearn and Hadley (1969) investigated the effects of tempera- ture and humidity on water loss in the laboratory. Hadley (1970)