APHIDES AND ANTS. 103 



are attacked by several species of Aphis. Ants do 

 choose such localities for their nests, In such cases 

 they are on the best of terms with the Aphides ; but 

 the latter are no more necessary to their economy than 

 the blind Coleoptera, Myriapoda, and the like, which 

 are commonly found intermixed with them. 



4. Many aerial Aphides are visited by ants whilst 

 feeding on the sap of plants. Honeydew is secreted 

 out of this sap by organs connected with their nectaries. 

 Captive Aphides, condemned to underground life, are 

 cut off from their usual food, and it is presumed they 

 can no longer secrete honeydew. 



Huber's cattle-lair theory is, therefore, unsatisfac- 

 tory. If Aphides are imprisoned after marauding 

 expeditions, it must be for a different purpose than for 

 collecting food. 



It will be unwise to put limits to the peculiar phases 

 of insect economy. Extraordinary ingenuity and 

 unexpected habits are continually pressing on the 

 observation of the entomologist. Perhaps the only 

 safe conclusion arrived at with reference to Aphis and 

 Formica is, that the latter is a considerable sugar con- 

 sumer, and that like Man, it also is a fosterer of pets 

 and favourites. 



In the tropical parts of India and Brazil, where 

 Aphides do not exist except on the high table lands, 

 ants show their appetite for sweets by thrumming the 

 sides of the larvae of certain species of Cercopis and 

 Menebracis (Coccidaa). In England I have often 

 noticed their resort to some of our Psyllida for the 

 same purpose. 



It is not a little remarkable that the friendly rela- 

 tions between Aphis and Formica have been of a very 

 ancient date. There are unmistakable evidences that 

 in the Middle Tertiary ages, when the Hymenoptera 

 were so largely represented by ants (far more so than 

 in modern times), the then existing Aphides were as 

 much frequented by them for their secretions as now. 



The Rhizobiinaa are all root-feeders; yet, as there 



