286 NATURE SKETCHES IN TEMPERATE AMERICA 



plant life from the downpouring rain in summer, the effect 

 of hail, wind, sudden lowering or elevation of temperature, and 

 finally the effect of sunlight and shadow. On the other hand, 

 these physical forces are seen operating every moment of time 

 over the face of the earth, exercising a powerful influence now, 

 as they doubtless have in the past, over organic life. These 

 facts tell us that the interrelation and interdependence between 

 organic life and the relation to their environment are forever 

 seeking adjustment. We note that the destruction of a large 

 number of one form of life may disarrange the adjustment of the 

 whole interlacing series in a given locality, because of the depend- 

 ence or predaceousness of one form upon another. The same 

 is true as to the effect of a sudden shower in summer, which 

 may cause the death of thousands of insects, to say nothing of 

 the occasional destruction caused in other groups of animals. 



Hinds says, in writing of Thrips, which are minute insects 

 often found on flowers and grasses, that "of all the natural 

 checks none can compare in efficiency with a hard dashing rain." 

 He further notes that these insects are "abundant during hot 

 dry weather, but disappear almost entirely as soon as the heavy 

 showers of midsummer begin, and as long as such showers 

 continue at frequent intervals, the Thrips do not again become 

 abundant." These observations might be multiplied without 

 number, showing the destructive effects of summer showers, 

 while other facts could be adduced to show their beneficial 

 action. Millions of small land animals suffer destruction 

 during every hailstorm in summer, and though these hail- 

 storms are quite local, the effect is nevertheless one that 

 influences the future generations and it may change the whole 

 interrelated system of life adjustments. 



The wind as a factor in local and geographical distribution 

 is evident to every observer who goes afield for the valuable 

 information there afforded. Aside from carrying hordes of 

 insect life adrift in the prevailing southwest winds in this 

 temperate latitude to new habitats, other hordes suffer destruc- 

 tion from the fact of not falling in their descent upon the earth 

 into a suitable environment. The seeds of plants profit by 

 the strong wind currents in being distributed into new fields, 

 but many of these fall on sterile ground. 



