| Summary |
Occurrence of beetles in manure samples was ascertained after 24, 48, 72 and 96 h exposure. At each interval, samples totally exposed, covered by large screen, and covered by small screen were investigated. Succession of beetles, diversity indices, and the effect of elimination of species by screening on succession and diversity indices were studied. Forty-four species of adult ColeĢ¤ptera from the families Histeridae, Scarabaeidae, Staphylinidae, and Hydrophilidae were recovered from uncovered manure samples from June through September, 1973. Of these beetles 14 have been identified as species not previously reported in North Carolina. The succession of ColeĢ¤ptera species followed a general predictable pattern. First, coprophagous hydrophilids arrived at the manure immediately after deposition and were followed by large densities of scarabs. After 48 h the coprophagous species began departing and predaceous species arrived in large numbers. In samples older than 72 h, few dung feeders were present in the semi-moist central core of manure and predaceous beetles increased in numbers. since bovine manure is typical of most microhabitats, in that it does not have a progression of stages to a climax, general diversity trends are atypical. Shannon-Weaver index values and the evenness and richness indices indicated environmental changes in the manure. The watery, nutrient rich manure was first inhabited by numerous coprophagous species and, during mid-summer, low index values reflected their extremely high densities. Intermediate stages of beetle succession, 48 to 72 h, had high richness values due to the mixture of coprophagous and predaceous species. Later stages,96 h, were characterized by the dominance of several predator species; thus low richness and high evenness values tended to lower the Shannon-Weaver index value. An overall reduction in density of beetles occurred and was attributed to the inaccessibility by some species to deeper areas of the manure due to a lack of tunnels. Predaceous species used the tunnels for better access to prey. Smaller hydrophilids were reduced by 80% and staphylinids by 78%. Two species, Aphodius haemorrhoidalis and Platystethus americanus, had higher densities in the large screened samples than in uncovered samples. Examination of seasonal occurrence patterns of these species indicated that both were found in higher densities in June before the great increases in other species. Thus, the increase in densities of both species in large screened samples indicated density dependent competition between some other species for a particular resource. The small screening further eliminated tunneling species. All other scarabs were eliminated in the small screened samples; some apparently crawled between the screen and the pans. The smallest hydrophilids, the staphylinids, and Phelister subrotundas were the only species small enough to enter through the screening. All but one of these beetles had reduced densities when compared with those of uncovered samples. Platystethus americanus alone had increased densities. The succession of species was altered as a result of the smaller screening. Those scarabs attracted by fresh manure were present, but the small hydrophilids appeared incapable of extended tunneling. The densities of some staphylinids increased in the small screened samples when compared with large screened samples. |
