Phenology and spatial pattern of Typhaea stercorea (Coleoptera : Mycetophagidae) infesting stored grain: Estimation by pitfall trapping

The hairy fungus beetle, Typhaea stercorea (L.), occurs frequently in store d grain, often in large numbers. Populations infesting stored barley in Min nesota. corn in South Carolina. and wheat in Florida were sampled by means of grain probe traps. Spatial distribution of the species was examined by c ontour analysis of trap catch. In South Carolina, corn was sampled at 2 loc ations over 2 storage seasons, and temperature, moisture content, and malat hion residues were measured. These data were used to examine phenology as w ell as spatial distribution. and showed peak trap catch shortly after harve st in the fall, and in the spring. This pattern followed seasonal changes i n grain temperature, but there was no apparent relationship of trap catch t o either grain moisture content or malathion residue. The populations of T. stercorea were not distributed randomly, but Mere largely concentrated in 1 or very few aggregations associated with the "spoutline," a region high i n foreign material and broken grain that forms near the center of a bin as it is loaded. However, the spatial patterns were dynamic, even on a very sm all time scale (week to week). Numbers of insects in aggregations rose and fell, the areas involved expanded and contracted, the centers shifted, and secondary centers appeared and disappeared. These changes were apparently i n response to changing patterns of grain temperature and moisture content. Secondary centers of aggregation often formed in warmer grain along bin wal ls.