Diversity and Seasonal Phenology of Coprophagous Beetles at Lake City, Michigan, USA, with a New State Record for Onthophagus taurus (Schreber) (Coleoptera: Scarabaeidae)

Surveys of insects from spring through autumn document the richness, abundance, and seasonal activity of species in a local area. Publication of these data provides historical records for use by future researchers to document changes in species diversity. To characterize the local assemblage of coprophagous beetles, dung-baited pitfall traps were operated in 2011 at the Lake City Research Center (44°18′35′′N, 85°12′11′′W), Michigan. Owned by Michigan State University, the Center is a 344-ha agricultural research farm with a herd of about 180 cows that are rotated among pastures during the grazing season. The area is characterized by sandy loam soil. Long-term climate data (Weatherbase 2012) for McBain, MI (11 km SE of Lake City) identify average high and low temperatures in the coldest month (February) of −1.9 and −12.9°C, respectively. Average high and low temperatures in the hottest month (July) are 27.2 and 12.4°C, respectively. Average annual precipitation is 741 mm. Pitfall traps were located at two sites (n = 20 traps/ site). Site A was a pasture that had been converted from pine forest five years prior to the study. Pastures adjacent to Site A have been in existence for 20–30 years. The absence of cattle at Site A allowed for the continuous operation of traps at the site throughout the study. Site B was not at a fixed locale, but rather was relocated to follow the movement of cattle among pastures. Pitfall traps for Site B were located adjacent to the pasture in use, approximately 3 m from fence lines to prevent disturbance by cattle. Sites A and B were always separated by less than 2 km. Within sites, traps were aligned in two rows 3 m apart. Within rows, traps were spaced at 3-m intervals. Traps comprised plastic cups (ca. 550 ml capacity) buried to brim-level in the soil. A wire mesh screen (1.27-cm grid) over the mouth of each cup excluded small animals and supported a dung bait. Dung baits comprised fresh cattle dung (ca. 75 g) wrapped in paper towel. Dung was collected on site from cattle untreated with parasiticides. Parasiticide residues in dung can affect colonization of pats by coprophilous insects (Floate 2007). Water (ca. 150 ml) containing a few drops of dish detergent was added to each cup to prevent the escape of beetles. Traps were emptied 48 hours after baiting. Trap catches for each combination of site and collection period were combined and preserved in 70% EtOH. Traps were operated every second week for a total of twelve trap periods beginning 15 May and ending 17 October. Specimens were identified by the first author with reference specimens in the Albert J. Cook Arthropod Research Collection (Michigan State University) and the assistance of Gary Parsons, the collection curator. The total collection comprised 10,041 beetles in 20 taxa (Table 1). Recovery of most species was expected, based on results of similar surveys in neighboring states (Valiela 1969; Cervenka and Moon 1991; Pimsler 2007). The recovery of adults for the most common species is presented by collection period in Fig. 1. The recovery of Onthophagus taurus (Schreber) is believed to be a new state record. Prior to the current study, there were no specimens in