80 ANIMAL LIFE AND SOCIAL GROWTH 



population becomes more varied and abundant. 

 There are more spiders, digging wasps, tiger 

 beetles, grasshoppers, snout beetles and flies of 

 various sorts. The trees themselves are attacked 

 by insect borers and by leaf feeding forms. All 

 these plants and animals add more humus to the 

 sand; as before, this is mixed through the upper 

 layers by the activity of the burrowing insects. 

 The grasses bind the dune increasingly more firmly 

 and conditions gradually are made more favorable 

 for the growth of bunch-grass and for the seed- 

 lings of a scrub pine. 



These pines develop until they come to dominate 

 a characteristic community in which other plants 

 are able to invade the dunes successfully, notably 

 the junipers. Spring flowers make their appear- 

 ance and the accompanying insect life becomes 

 still more abundant. The six-lined lizard, and 

 turtle from the nearby ponds, bury their eggs 

 in the sand; blue racer snakes place theirs under 

 rotting logs. White-footed mice, ground squir- 

 rels and rabbits breed here; common grouse nest 

 on the ground and woodpeckers make their nests 

 in the trees. The pines are attacked by a multi- 

 tude of borers. Their needles form a thick mulch 

 over the sand and in a relatively short time the 

 soil has been built up sufficiently for an invasion 

 of black oaks. 



