THE FOSSORS OR DIGGERS 21 



etc.; many of these, when they leave their bur- 

 rows, throw up some sand over the hole so as 

 completely to cover it ; how these insects find 

 the spot again after a lengthy chase after 

 spiders or other prey is a marvel ; and yet 

 those who have observed carefully say that 

 they come home from long distances with 

 unerring precision. No sense of which we 

 have any knowledge, however accentuated, seems 

 to explain this. To be able to arrive back at a 

 home in an extensive arid sandy plain, where no 

 outward sign indicates its whereabouts, must 

 surely require perception of a different nature 

 from any of those with which we are endowed. 

 Some fossors are subject to the depredations of 

 cuckoos, just as the solitary bees are, but their 

 cuckoos are rarely of aculeate origin. The 

 only ones which I have had any opportunity of 

 studying are the species which nest in bramble 

 stems. The cuckoos which associate with 

 them are some of the smaller jewel flies and 

 Ichneumons : the habits of both these differ 

 from those of the aculeate cuckoos, the jewel 

 flies devouring the larva of the aculeate and the 

 Ichneumon laying its eggs in it. The fossors 



