119 



McUiy kinds of insects are recorded as "sleeping" among rank 

 growths of vegetation and on flowers. In such places on cloudy or cool 

 days, late in the evening or in the early morning, insects are found at 

 rest and in a sluggish or torpid condition. The cause of this behavior 

 is not known. They may be "sleeping," or they may only have been 

 trapped there by a lowering of the temperature, as at sundown, when 

 their activity slowed down and they came to a rest on the last flower 

 visited. In this connection it should be recalled that it is near the gen- 

 eral level of the surface of the vegetation that the most extreme tem- 

 peratures are found, — the most warmth in the sun and the greatest 

 coolness at night. This is the main zone also of flowers visited by in- 

 sects. 



In this same layer of vegetation is found the usual grouping of 

 vegetable feeders, scavengers, predators, and parasites. As the nectar- 

 drinkers visit the flowers, certain predators spring upon them, just as 

 the large members of the cat family seize their prey at the margins of 

 streams and lakes when the herbivores come to drink. Other preda- 

 ceous insects such as the wasps, robber-flies and dragon-flies, live 

 active lives and seek their prey on the wing. 



Above the general surface of the prairie vegetation no inverte- 

 brates live permanently, unless the parasites, external and internal, 

 of the swifts and swallows can be so considered. Winged forms fre- 

 quent this region during flights in which they find food and mates. 

 Spiders, by their cottony "balloons," utilize the winds and are thus 

 transported. All of these are transients, and not permanent inhabi- 

 tants of the open area. 



J. Interrelations zvithin the Prairie Association 



In concluding this discussion of the conditions of life on the prairie, 

 we may profitably consider some parts of the network of interrelations 

 which bind together the animals and the environment. As the kinds of 

 animals and the number of factors involved are so numerous, only a 

 few selected animals will be considered. In this choice I have not lim- 

 ited myself solely to the kinds taken at Charleston, but have utilized 

 common and well known prairie animals. As representatives of the 

 soil-inhabiting forms the white-grubs and May-beetles (Lachnos- 

 terna) and the corn-field ant (Lasius niger americanus) have been 

 chosen ; as representatives of those which live above the surface and 

 mainly among the vegetation the differential grasshopper and Bom- 

 hits have been chosen ; and as representatives of the active predators 

 and parasites, Promachus, Chlorion, Tiphia, and the parasitic fungi 

 Bmpusa and Cordyceps. Statement of the available supply of water 



