no A NATUILiLIST IN THE GREAT LAKES REGION 



material for the house is here. The cKff swallow prefers natural 

 rock walls beside the water to which to afhx his mud jugs for 

 nesting purposes. The woodpecker must live in the forest, not 

 only because his food is there, but also because he needs a tree 

 for his nest site. The marsh wren away from the marsh would 

 probably find it more difficult to find substitute for the rushes 

 she uses to make her globular nest (see Fig. 345) than she would 

 to secure her insect food. Shelford found that, giving the tiger 

 beetle, which is found on the clay bluffs along the shore, oppor- 

 tunity in the laboratory to 

 deposit eggs on steeply in- 

 clined and level clay, sand, 

 and loam, in all cases the 

 females chose the clay in 

 which to deposit the eggs 

 and that two-thirds of the 

 holes made in oviposition 

 appeared on the steep clay. 

 Complex adaptations, both 

 of structure and of habit, 

 have arisen in connection 



Fig. 67.— Digger wasp of the Dunes, with the USe of specific loca- 

 Bcmbcx spimlae, X4. Below, the front tions or of particular mate- 

 foot, Xio. j^^jg -j^ j^gg^ building. A 



single instance must here suffice. In the cottonwood zone 

 in the Dunes there is a digger wasp that excavates a burrow 

 in the sand in which to deposit its eggs (Fig. 67). The 

 wasp is a httle larger than a house fly. It stands on the 

 sand to dig, and proceeds very much like a dog digging a 

 hole in the ground. It uses the forefeet as excavating tools 

 and throws the dirt out from under its body between the 

 hmd legs. It makes the dirt fly, too, at a great rate. The 

 animal's front foot is expanded and provided with bristles along 

 the edge that further enlarge it and make quite an efficient 

 digging tool. The burrow usually starts on a sloping hillside 



