Author's Preface 



My cages have a capacity of about a cubic 

 yard. Except for the front, which is of wire 

 gauze, the whole is made of wood. This 

 keeps out any excessive rain, the effect of 

 which would be to turn the layer of earth 

 in my open-air appliances into mud. Over- 

 great moisture would be fatal to the priso- 

 ners, who cannot, in their straitened artificial 

 demesne, act as they do when at liberty 

 and prolong their digging indefinitely un- 

 til they come upon a medium suitable to 

 their operations. They want soil which is 

 porous and not too dry, though in no danger 

 of ever becoming muddy. The earth in the 

 cages therefore is of a sandy character and, 

 after being sifted, is shghtly moistened and 

 flattened down just enough to prevent any 

 landslips in the future galleries. Its depth 

 is barely ten or eleven inches, which is in- 

 sufficient in certain cases; but those of the 

 inmates who have a fancy for deep galleries, 

 like the Geotrupes for instances, are well able 

 to make up horizontally for what is denied 

 them perpendicularly. 



The trellised front has a south aspect and 

 allows the sun's rays to penetrate right into 

 the dwelling. The opposite side, which 

 faces north, consists of two shutters one 

 above the other. They are movable and 



xvii 



