128 MOUNTAIN AND MOORLAND 



moisture below the surface of the soil. If the sand 

 were all dry and powdery the walls of the shaft would 

 always be falling in. Another interesting point is that 

 the lower part of the larva's head forms a hard rounded 

 knob, which is used in the most deliberate way to 

 make the wall of the burrow smooth. One may almost 

 say that the Tiger grub has anticipated the plasterer 

 as well as the miner. 



The Tiger grub is a carnivore with a big appetite, 

 but it never leaves the burrow, and its mode of captur- 

 ing its prey is unique. There are hooks on a dorsal 

 protuberance on one of the segments of the grub-like 

 body, and these serve for attachment to the wall of 

 the shaft. The larva fixes itself so that the shield- 

 shaped top of its head forms a sort of door or lid 

 across the shaft just a little below the surface. A 

 small Spider or a little Insect, such as an Ant, comes 

 along, and investigating the depression steps on the 

 lid. The Tiger grub is not in a hurry, and yet it loses 

 no time. When the Spider or the Ant is quite on the 

 top of the grub's head, this is suddenly jerked back- 

 wards against the wall of the shaft and the victim is 

 probably killed outright. It is then gripped in the 

 larva's jaws. If the Ant slips down into the burrow, 

 it has to come up again, and it is not likely to 

 escape a second time. Dr. Stager has given a wonder- 

 ful description of the spring-like violence of the head 

 jerk by which the small insect is battered to death. 

 When it has killed its victim, the Tiger grub descends 

 the shaft and sucks out the juices. The dry husk is 

 afterwards thrown out with a jerk. 



