FIG. 8-9 Burrows made !n sand 

 by arthropods, (a) burrows of 

 a digger wasp, Microbembex 

 monodonfa. (b) a digger wasp, 

 Bembex spinolae, and a cross- 

 section sketch of its burrow 

 (Sheiford 1913). (c) the white 

 tiger beetle and its burrow 

 (Sheiford 1913). (d) excavated 

 burrow of a sand spider (courtesy 

 R.E. Rundus). The upper portion, 

 shown with a stick in it, is 

 intact; the lower portion, in the 

 shadow, is broken open. 



U 



nil 



in the trees. Tracks of the prairie deer mouse 

 are frequently to be seen on the sand. Fowler's toad 

 and the hognose snake are the only amphibian and 

 reptile that regularly occur. The grass, slirub, and 

 Cottonwood stages ordinarily occupy relatively nar- 

 row belts parallel to the lake shore. Extensive sandy 

 areas inland may have a larger variety of species 

 present (Vestal 1913). 



The pine community in the sere is not so well de- 

 /eloped around the south end of Lake Michigan as 



it is northward. The coniferous forest penetrates 

 southward from the north, and some northern ani- 

 mals move with it. Nesting birds are represented by 

 the slate-colored junco, red-breasted nuthatch, black- 

 throated green warbler, blackburnian warbler, and 

 myrtle warbler, all belonging to the boreal forest 

 biociation. Forest-edge and deciduous forest birds 

 also occur. The red squirrel is a characteristic boreal 

 mammal that occupies this stage, and the white-tailed 

 deer browses on conifer foliage, especially the white 

 cedar. The six-lined racerunner and blue racer snake 

 appear. Among the invertebrates are the bronze tiger 

 beetle C. scntellaris and the ant-lion. 



With the advent of the black oak and later forest 

 stages, most species requiring open areas or depend- 

 ing on patches of bare sand disappear. Although the 

 bronze tiger beetle remains abundant in the black oak 

 community, it, as well as the other tiger beetles, 

 disappear in the higher plant stages. Only the green 

 tiger beetle C. sexguttata is in the climax, a species that 

 requires bare spots on the forest floor, but not sand. 



Reptiles are not common in the sand sere around 

 Lake Michigan, but elsewhere around the world liz- 

 ards and snakes are quite characteristic of sandy 

 habitats. They are remarkable in showing a variety 

 of structural and behavioral adaptations specific to 

 locomotion in sand and for protection of their sense 

 organs and body openings from sand (Mosauer 

 1932). The sidewinder rattlesnake, for instance, has 

 evolved, in addition to the usual undulatory lateral 

 movement of snakes, a rolling sidewise movement 

 that involves spiral contractions of the body and ap- 

 plies vertical rather than lateral pressure to the sand. 

 Sand offers the snake an unstable footing — lateral 

 undulations alone do less to propel the snake forward 

 than to merely push sand aside. Sand provides firm 

 footing only if it is pushed down upon, hence the 

 effective, if singular, action of the sidewinder. 



110 Habitats, communities, succession 



