摘要：Dytiscid beetles were surveyed to establish a baseline list for this county, which lies primarily in the Mississippi Alluvial Plain. This list was then compared with that for an Ozark county, which had been surveyed in a previous study. Eighteen sites were surveyed by Turtox Indestructible ™ dip net and funnel traps. Museum holdings and literature records were also searched. Twenty-one taxa were collected, with temporary ponds and oxbow/cypress swamps supporting the greatest diversity. These are the least disturbed sites in Jackson County. Most species collected are generally widely distributed and prefer either shaded ponds/pools with some leaf litter, or shallow areas of ponds, lakes and slow streams. To the contrary, Randolph County, on the Ozark Plateau, has more taxa (31), with many typifying Ozark streams. More specifically, Hydroporus was represented by seven species in Jackson County, but 13 species were found in Randolph County. The difference was the presence in Randolph County of the subgenus Heterosternuta, found invariably along the gravelly margins of clear streams.
