The Geotrupes: Nest-building 



but a day's sunshine is enough to dry the soil 

 to the shallow depth where the Geotrupes' 

 nest lies. It is a serious matter not to lose 

 the enjoyment of this fine day. How will 

 the grub benefit by it? 



Imagine the larva enclosed In the big ball 

 which the copious quantity of food placed at 

 its disposal might well supply. Once satu- 

 rated with moisture by a shower, this sphere 

 would retain it stubbornly, for its form is 

 that of least evaporation and of least contact 

 with the sun-warmed soil. In vain, within 

 twenty-four hours, will the surface layer of 

 the ground be restored to its normal coolness : 

 the globular mass will retain its excess of 

 water, for lack of adequate contact with the 

 sun-and-air-dried earth. In the too-humid 

 and too-thick recess, the provisions will go 

 musty; the heat from outside will be inoppor- 

 tune, as will the air; and the larva will derive 

 little advantage from this late autumn sun, 

 whose tardy rays ought to ripen it to perfect- 

 ion and give it the necessary vigour to brave 

 the trials of winter. 



What was a good quality in July, when It 

 was necessary to guard against excessive dry- 

 ness, becomes a bad one In October, when 

 excessive damp is to be avoided. The cylin- 

 der is therefore substituted for the sphere. 



303 



