INTERRELATIONS OF INSECTS 339 
Oo 
the sake of which the ants carry on their complex oper- 
ations consists of the knobbed ends of fungus threads 
(Fig. 285), and these bodies, rich in fluid, form the most 
important, if not the sole food of the leaf-cutting ants. By 
assiduously weeding out all foreign organisms the ants ob- 
tain a pure culture of the fungus, and by pruning the fungus 
they keep it in the vegeta- 
Fic. 285. 
tive condition and prevent 
its fructification; under 
exceptional circumstances, 
however, the fungus devel- 
ops aerial organs of fructi- 
fication of the agaricine 
type, but this species (/o- 
zites gongylophora) has 
never been found outside 
of ants’ nests. The pecu- 
liar clubbed threads were 
produced by Moller in arti- FUEOS Cluimpsien CRoMiesecozalanioeal 
Meimrcwituressand are: mot ~cutvated by ants .of the sgouus9 ane 
Greatly magnified.—After MOL.eEr, 
‘spores, but products of cul- 
tivation. Other ants are known to cultivate other kinds of 
fungi for similar purposes. 
McCook has found a leaf-cutting ant (Atta fervens) in 
Texas, and mentions that it cuts circular pieces out of leaves 
of chiefly the live-oak, these being dropped to the ground and 
taken to the nest by another set of workers. He records an 
underground tunnel of Atta fervens which extended 448 feet 
from the nest and then opened into a path 185 feet in length; 
the tunnel was 18 inches below the surface on an average, 
though occasionally as deep as 6 feet, and the entire route led 
with remarkable precision to a tree which was being defoliated. 
The same observer has given also a brief account of a leaf- 
cutting ant that lives in New Jersey. This species (Atta sep- 
tentrionalis) cuts the needle-like leaves of seedling pines into 
little pieces, which are carried to the nest. “Two columns of 
