214 DRY AND MESOPHYTIC FOREST COMMUNITIES 



green form (Fig. 167), appears in the autumn and lives over winter in 

 the ground (151). 



The tiger-beetle larvae are found on the bare spots and sometimes 

 among the sweet clover (eggs are laid before the clover is full grown). 

 They feed on any animals that crawl over the clay within reach any 

 that we mentioned may fall victims. 



As physiographic processes go on, we find that more animals make 

 their appearance, bristle-tails creep out of the cracks in early spring, and 

 occasional slugs and geophilids are found hiding under clods. A large 

 black spider (Pardosa lapidicina) (138) (Fig. 168) and many smaller 

 species are present also. More rarely one of the land snails (Pyramidula) 

 is present at this time of year, crawling about under the dead vegetation. 

 The mud-dauber wasp (Pelopoeus cementarius) secures its mud (40) 

 and the Carolina locust (Dissosteira Carolina) probably breeds here. 



b) Field stratum. Under such conditions, as summer advances the 

 sweet clover grows up, and as soon as it is of considerable size it is 

 attacked by aphids, which form the basis for a small consocies of inter- 

 dependent animals. Many coccinelids come to feed on aphids, and 

 parts of adult coccinelids have been found in the burrows of the tiger- 

 beetle larvae. The golden-eyed lacewing (Chrysopa oculata) deposits 

 stalked (p. 291) eggs on the plant; soon its larvae the aphis-lions 

 are devouring aphids, as do also the larvae of syrphus flies (164). 



Crab-spiders (Runicina aleatoriQ, Misumena vatia) (138) lie in wait 

 in the clover flowers and thus capture the nectar- and pollen-seeking 

 flies, such as Eristalis tenax (Fig. 271, p. 270) and Syrphus ribesii Lin. 

 (165). The common plant-bug (Adelphocoris rapidus) (Fig. 262, p. 266) 

 is especially abundant in autumn. The honey-bee (Apis mellifera) and 

 a bumblebee (Bombus americanorum] come in numbers for nectar and 

 pollen. Grasshoppers, such as Scudderia, Melanoplus femur-rubrum, 

 etc., are common, and when young may fall prey to spiders such as orb- 

 weavers (Epeira trivittata) . Parasitic hymenoptera (Pimpla conquisitor 

 Say) are also common. 



3. SHRUBS ASSOCIATION (A FOREST MARGIN SUB-FORMATION) 



A little humus accumulates locally through the decay of sweet 

 clover. The roots of plants in the soil and the undecayed trunks of 

 the sweet clover hold this and the mineral soil in place against the 

 action of the rain as it falls on the slope. Conditions become ripe 

 for the germination of the seeds of other plants and for the breeding 

 of other animals. Shrubs, such as the willow and shad-bush, appear 



