Mutualism without Continuous Contact 371 



the winter until they hatch and the young aphids repopulate the dairy 

 farm (Fig. 10.5). 



An equally extraordinary agricultural technique practiced by in- 

 sects is the cultivation of fungi by certain beetles, ants, and termites. 

 Various kinds of fungi are grown for food by these animals, and some 

 species are known only in insect gardens of this sort. In the tropical 

 forest one may see a band of green moving across the ground; this is 

 formed by a line of leaf-cutting ants {Atta) carrying pieces of leaves 



Fig. 10.5. Diagram of an ant nest containing a "dairy farm" of aphids. (Burk- 

 holder, 1952, Copyright, Baitsell's Science in Progress, Yale Univ. Press. ) 



over their backs like so many umbrellas. The leaves have been cut 

 from a shrub and are being transported to the ant's underground nest 

 where they will be chewed into a pulp and spread out to form a bed 

 in which a particular kind of fungus (Rozites gongylophora) is 

 planted. The ants cultivate the garden with great care; they weed 

 out unwanted species of fungi and prevent the fruiting of their 

 fungus, but encourage it to develop special mycelial outgrowths on 

 which they feed ( Brues, 1946 ) . The fungi that live symbiotically in 

 termite nests are nourished by the insects' excreta rather than by leaf 

 pulp. The cultivation of fungi by ambrosia beetles (Scolytidoe) is 

 carried on within the tunnels drilled in wood by these insects ( Cham- 



