The red-bellied snake, Storeria occipitomaculata, is a small, fossorial thamnophiine snake with a disjunjct distribution that includes the area from eastern North Dakota to Nova Scotia, south to Florida, and west to eastern Texas. Speculation that the Great Plains acts as a barrier to westward dispersal has been hypothesized, due to the fact that they are absent from large areas of remnant prairie in the midwest and east, an idea that goes back to the work done by Harold Trapido in the 1940's. This hypothesis appears to be wrong, Bown and Phillips examined 387 preserved specimens, literature records, and unpublished data and found the species is distributed throughout much of the state of Illinois. Their study suggests red-bellied snakes do indeed inhabit woodlands but that they are not adapted for primary forest, and the authors found they do in fact use prairie and prairie-like habitats. Brown and Philips suggest red-bellied snakes are adapted for cool to cold envuironments ands that they inhabited the ice rim of the Wisconsin glacial episode, following the ice northward as it retreated. Evidence for this comes from the snakes distribution in northern prairies and coniferous forests.
Brown, L.E. and C.A. Phillips. 2012. Distribution, habitat, and zoogeography of the semifossorial red-belied snake Storeria occipitomaculata (Storer) in Illinois. Illinois Natural History Survey Bulletin 39 (5):297-322.