SEASONAL-VARIATION OF SAP BEETLE (COLEOPTERA, NITIDULIDAE) POPULATIONS IN CENTRAL ILLINOIS CORNFIELD-OAK WOODLAND HABITAT AND POTENTIAL INFLUENCE OF WEATHER PATTERNS

Species of sap beetles present at a central Illinois cornfield-oak woodland habitat were determined by spring to fall collections from can traps baited with fermenting wheat dough and banana. Carpophilus lugubris Murray was the dominant species. Glischrochilus quadrisignatus (Say) and Stelidota geminata (Say) were also collected frequently. Other species collected commonly were C. antiquus Melsheimer, C. freemani Dobson, and Colopterus truncatus Randall, which were generally encountered only in the early spring and late fall. Peak collections of C. lugubris were in late April, early June, and throughout the fall. A similar trend was noted for G. quadrisignatus, but S. geminata only had late spring and fall peaks. The peaks occurred at fairly consistent intervals over all 3 yr for G. quadrisignatus and S. geminata, but the spring first generation peak for C. lugubris was retarded by 3-4 wk during 1988. This change in population distribution might have resulted from the long dry period that occurred during this time.