Studies on the relative abundance and population fluctuations of insects occurring in the agricultural experiments and research Station of the King Saud University at Dierab, South Riyadh, were carried out from September, 2009 to December, 2010 using: Hand Picking, Malaise Traps, Pitfall Traps and Sticky Traps methods. The survey revealed the presence of one hundred sixty-two species belonging to one hundred twenty-eight genera, of sixty-two families under nine orders, (Coleoptera, Dermaptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera, Mantodea Neuroptera and Orthoptera). A total number of 1550 insects were obtained throughout the year. The largest numbers of individuals were observed during May, April and June. The largest number of species were found belonging to the order Coleoptera (81 species), followed by the hemipterans (16 species). Other orders were represented by varying number of species.
The coleopterans were found to be the most abundant and dominant, constituting the majority of the catch (1112 specimens, representing 71,7 % of the total catch), followed by hemipteran individuals (215 specimens, constituting 13.9 % of the total catch). Insects of other orders were less abundant and were represented by small numbers of individuals, with the Mantodea and Dermaptera constituting the minority of the catch (one specimen of one species) for each and Neuroptera (nine specimens of three species).