Species composition and seasonal abundance of Aphodiine dung beetles (Coleoptera: Scarabaeidae) in dung from ivermectin-treated and nontreated cattle

Aphodiine beetles were collected from the dung of ivermectin-treated and nontreated pastured cattle during the spring and summer months of 1993 and 1994. Seven aphodiine species in the two genera Aphodius and Ataenius were found in both ivermectin-contaminated and noncontaminated dung in both years. In 1993, over 8,200 aphodiine beetles were collected, and approximately 3,000 aphodiine beetles were collected in 1994. The percentages of the total collected numbers for each species in 1993 and 1994, respectively, were: Aphodius haemorrhoidalis 83.16% and 64.90%; Aphodius lividus 3.88% and 2.70%, Ataenius platensis and Ataenius spretulus (combined together in 1993) 7.24%; Ataenius platensis 0.07% (1994); Ataenius spretulus 1.37% (1994); Aphodius fimetarius 1.27% and 5.93%; Aphodius stercorosus 2.67% and 5.67%; and Aphodius erraticus 1.78% and 19.37%.

About twice as many specimens were collected in ivermectin-contaminated dung (66.26%) as compared to noncontaminated dung (33.74%) in 1993, and the following year twice as many were again collected in ivermectin-contaminated dung (67.76%) as compared to noncontaminated dung (32.24%). Statistical analysis indicates that ivermectin itself did not affect the densities of individual species in either dung type. However, in 1993 the combined data of the three most abundant species (Aphodius haemorrhoidalis, A. lividus, and Ataenius platensis and A. spretulus added together) showed they were significantly more abundant in ivermectin-contaminated dung, but the combined data of the three most abundant species collected in 1994 (Aphodius haemorrhoidalis, A. fimetarius, and A. erraticus) show no significant differences between densities in either dung type. Statistical analysis of the combined influence of treatment and the week in which samples were collected post-treatment are presented and discussed.

Seasonal distributions in 1993 and 1994 are presented for 6 of the 7 aphodiine species (except Ataenius platemis), based on the numbers of specimens collected in noncontaminated dung. In addition, the potential impact of ivermectin treatment on aphodiine beetles is discussed.