A 2-yr study (1971-73) in the Sierra Nevada foothills of California consisted of: 1) a quantitative analysis of the differences in diversity and abundance of the insect fauna colonizing and inhabiting diurnally and nocturnally excreted cattle droppings in four different pasture and rangeland ecosystems (natural woodland range, partially cleared woodland range, totally cleared woodland range, cultivated irrigated pasture); and 2) a study of the relationship between the diversity and abundance of insect inhabitants per cowpat and the rate of pat degradation.

The fauna consisted of three orders of insects containing 26 families and 102 species. There were 35 to 40 different kinds of Coleoptera, 50 of Diptera, and 12 of Hymenoptera, recorded from samples.

Differences per pat in the mean number of species, number of individuals, and insect biomass among pastures, months, and years for the major taxa were analyzed and discussed. The pasture ecosystem and the season were most important in determining the diversity and abundance of insects colonizing droppings. Major differences among pastures in the number of individuals and species per pat were mainly due to a combination of interacting loco-and microclimatological factors associated with the environment of the different pastures. Most species of dung insects did not colonize pats dropped during the night.

The most important insect species influencing biomass per pat was the scarab, Aphodius fimetarius (L.). The importance of considering species, individuals, and biomass in attempting to understand changes in community structure and function was demonstrated.