54 BULLETIN 647, U. S. DEPARTMENT OF AGRICULTURE. 



The ants soon began tunneling into the ground at short intervals 

 along the entire course of the trail, and by October 15 these shafts 

 were numerous. The foragers still followed the original trail along 

 the surface of the ground, but could no longer be traced for its 

 entire length, as they were continually disappearing into the tunnels. 

 Queens gradually separated from the original colony and took up 

 their abode in the tunnels, until finally there was a string of small 

 colonies all along the trail from mother colony to sirup. The origi- 

 nal purpose of the tunnels doubtless was to protect the workers from 

 light and heat while they rested from their labors, but the queens 

 found them well adapted for nesting purposes. 



SHELTER STRUCTURES, OR " COW SHEDS." 



In the trees the ants invariably utilize such natural shelters as 

 cracks and depressions in the bark, abandoned tunnels of borers, the 

 space between touching leaves and fruits, etc., often further exclud- 

 ing light by piling particles of trash along the edges of cracks and 

 walling in the space between nearly touching leaves, fruits, and 

 branches. A portion of the ants foraging in trees almost invariably 

 may be seen retracing their steps up the tree, carrying either liquid 

 forage or prey with them. If traced, these ants usually will be 

 found seeking a rest in the nearest shelter of the sort mentioned. 

 Sometimes, while resting, their forage is deposited nearby and occa- 

 sionally thereafter forgotten ; at other times it is held indefinitely in 

 the jaws. 



The erection of the so-called " cow sheds " over scale insects and 

 aphids is a further extension of this habit of building shelters in 

 which the worker ants can rest. The number of ants attending 

 aphid and coccid groups is almost always greater than can secure 

 honey dew continuously. Some of them, therefore, always must be 

 waiting until their hosts have a fresh supply ready. During this 

 period of waiting and unrequited solicitation the " cow sheds " serve 

 the usual ant-protective purpose. These structures, of course, may 

 protect from enemies the particular insects covered by them, but, 

 even if this protection were absolute, no great number would benefit 

 by it, because comparatively so few are covered. The occasional 

 occurrence of parasitized remains of scales under these " cow sheds " 

 indicates, furthermore, that the protection afforded even those com- 

 paratively few scales is often faulty. 



On orange trees badly infested by the black scale shelter structures 

 sometimes are found over groups of mealybugs, and in this case their 

 most important function happens to be protection of the ants and 

 mealybugs against the honeydew of the scale and its accompanying 



