xiv ON SAFARI 



177 



to Lake Nakuru, the grass over a large part of the 

 country liad l)eeu set 011 five, and in many directions it 

 was burning liriskly. In the districts traversed hy our 

 porters several elliptical areas of jilain soil among the 

 lilackened grass attracted my attention. These patches 

 measured in most instances three yards in the major 

 and two in tlie minor axis : they v/ere sunk slightly 

 helow the level of the surrounding ground and were as 

 free from grass as a newly-polished tombstone, and the 

 surface was as smooth as if it had lieen finished by a 

 plasterer's trowel. In the first instance I was interested 

 in these smooth patches because on many of them we 

 found game tracks, such as footprints of the impalla, 

 water-buck, hartebeest (kongoni), or the rhinoceros. 

 These footprints stood out as plainly as the imprints of 

 a hare, polecat, or rat on snow-coveretl ground. 



Un examining the bare patches more carefully, I 

 found two or three circular holes surrounded by a ridge 

 of dust, an inch high, from which brown ants issued; 

 near the edge of the patch there was a heap of husks, 

 and on examining them they proved to be the husks of 

 many varieties of grass seeds. When the patch was 

 situated in an area where the grass had been closely 

 burnt it was easy to make out ant-paths radiating 

 in many directions from the clear area, and the ants 

 laden with seed could be seen travellino- alono- them. I 

 have re-read carefully Moggridge's description of 

 harvesting-ants ; I have no doubt that these elliptical 

 jjatches of grass-free ground are due to the energy of 

 some species of these interesting and industrious insects. 

 The smooth appearance of the patch is due to the 

 persistent traffic of multitudes of these small insects. 



It is curious that the grass and other seeds in these 

 undero-round o-ranaries do not germinate. No satis- 

 factory explanation has yet been advanced to account 

 for this fact, and I have no theory to offer. These 

 elliptical ant-grounds were numerous in the grass land 

 around Lake Nakuru. They were clear of small stones, 



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