460 LAND ANIMALS 



that scatter poisons from airplanes over adults or over their breeding 

 places. Grasshoppers and their relatives are particularly important 

 because they transform the hard grass of the summer steppe into easily 

 digested materials and so provide nourishment for a large number of 

 animals. 



Scorpions and solpugids, lizards, many snakes and turtles, hawks 

 and owls, marabous and storks, guinea fowl and ravens, and many 

 others feed upon grasshoppers. Hosts of buzzards follow the swarms in 

 South Africa, and the rosy starling (Pastor roseus) is drawn far from 

 its normal distribution area during the grasshopper years in pursuit of 

 the swams; grain-eating birds feed them to their young. Their scarcity 

 during the dry season is an important cause of bird migration in 

 Africa. 54 Many mammals also take grasshoppers as food, from the 

 weasel to the jackal, baboons, and man. 



The wood-devouring termites also feed on dry grass, and so find 

 abundant food, year in and year out, in the subtropical arid regions. 

 They construct their dwellings in the dry earth and heap up the exca- 

 vated material in the form of much-perforated domes like mole hills, 

 which rain and wind level off, or they cement these earth structures 

 into firm, sometimes enormously large, "anthills," the form of which is 

 characteristic of the individual species. The shape of the termite 

 mounds is extremely varied: flat plates, spherical, bluntly rounded 

 heaps of earth, conical and sugar-loaf towers, single or in groups, and 

 the wall-like compass nests which have already been mentioned. Such 

 constructions may reach a height of 4 m., and even 6 m., in many 

 species; Livingston indeed estimated some to be up to 9 m. in height. 

 They are almost impenetrable to rain and may even withstand tropical 

 hurricanes. A rich fauna is associated with these structures. Hostile 

 ants conquer a part of the stronghold and establish their nest in it, as 

 do other insects, especially carabids, like Anthia guttata in South 

 Africa. Numerous amphibians, lizards, and snakes feed exclusively on 

 the termites. Various mammals burrow into the termite structures, 

 like the jackal (Canis mesomelas), mongoose, and the aardvark 

 [Orycteropus) . 55 Monitor lizards lay their eggs in the nests. They 

 serve as alighting places for birds of prey as they search the plain for 

 food ; antelopes use them as shade for their noonday rest in the treeless 

 steppe. 



Ants are found in the ground as abundantly as the termites, but are 

 more widely distributed. Being eurythermal and euryhygric in con- 

 trast to the stenothermal, stenohygric termites, they range also into 

 the areas of cold winters. As long as the temperature permits, they are 

 active and continue to feed throughout the year in the subtropical and 



