150 A NATURALIST IN THE GREAT LAKES REGION 



face the intruder. The larva lives in a burrow in which it is 

 supported at the top by a spiny hump; the huge jaws fill the 

 orifice ready to seize any insect that unwarily steps on the living 

 trap. The jaws are approximately ground color so that you are 

 sometimes aware of the presence of the burrows when what was 

 at first solid ground becomes porous as the numerous larvae drop 

 back into their holes on your alarming approach. 



That the dune area is prolific in animal life may be realized 

 from the result of an animal census taken in midsummer by 

 Miss Nell Saunders, whereby she found in a mixed area of swale, 

 cottonwoods, and oaks sixteen million animals to the acre. This 

 population was distributed as follows : three-quarters of a million 

 on the ground stratum, three million on the herbaceous plants, 

 ten million on the shrubs, and the remainder on the trees. It is 

 evident from this and from the descriptions to follow that there 

 is a vertical zonation of life as well as a horizontal one. 



The succeeding societies of animals beginning with those near- 

 est the shore are, in the Dunes, as follows: (i) The predatory 

 ground beetle association corresponding to the beach association 

 of the plants. (2) The digger wasp association, corresponding to 

 the fore-dune and cottonwood zones. (3) The bronze tiger asso- 

 ciation corresponding to the transition zone between the cotton- 

 wood and pine areas and the pine association. (4) The ant-lion 

 association, equivalent to the black oak plant association. (5) 

 The hylodes association, corresponding to the mixed oak plant 

 zone. 



While both the wet beach and the storm beach (Fig. 83) are 

 practically free from plants, they are inhabited by characteristic 

 animals. When a strong offshore wind is blowing, hundreds of 

 species of insects and many birds from the territory adjacent to 

 the lake blow out over the water during their incautious flights 

 and drop exhausted to its surface. When the wind shifts, as it does 

 almost daily, the onshore wind piles. these animals, together with 

 dead fish, in long windrows on the beach. Some of the insects 

 survive their prolonged immersion and crawl under stones, chips, 



