| A complete arthropod community was investigated by pitfall traps and emergence boxes from 1991 to 1993. Over 60,000 invertebrates were collected in pastures. Arthropods found were 226 species belonging to 73 families in 14 orders. Coleoptera were the most diverse as judged by trapping and extracting (109 species), Diptera the second (35 species) and Hymenoptera the third (24 species). Most of the beneficial insects were in these three orders.;Field mortality of horn flies caused by the arthropod community was tested by seeding horn fly eggs underneath artificial cowpats, which were either exposed or isolated from the arthropod community by using cone traps. The community-caused mortalities of horn flies in the field were 75.9% and 66.7% in July and August 1992, respectively. The overall average was 71.3%.;Predation rates were tested under laboratory (Petri dishes) and simulated field conditions (test cages containing artificially formed pats) with adults of five field-collected Philonthus species against horn fly immatures. P. longicornis had the highest predation rate. Aleochara notula was very abundant during the survey and its adult is an effective predator of horn fly immatures. Fifteen other staphylinid, one hydrophilid, one histerid, and two carabid species were also found to prey on horn fly eggs and larvae. Larvae of eight staphylinid species and one tenebrionid species were also found to prey on horn fly immatures.;Red imported fire ants (RIFA) were observed to infest cowpats heavily all year round and prey on horn fly larvae and pupae in the pastures. RIFA caused 94.3% and 62.9% mortality of horn flies, respectively, for October 1992 and 1993, compared with a RIFA-controlled area in the field, though it reduced populations of horn fly natural enemies. |
