RELATIONS OF AN 1'S TO OTHER INSKCTS. 



34* 



from some other mysterious source, is voided by the droves of plant- 

 lice. Within more recent years this subject has been exhaustively 

 studied by Biisgen (1891). The quantity of honey-dew excreted by 

 the aphids, when we consider the small size of these insects, is most 

 surprising. Biisgen found that a single linden aphis excretes nineteen 

 drops in twenty-four hours, while the maple aphis excretes as many 

 as forty-eight drops during the same 

 period. A source of nutriment at once 

 so rich and so inexhaustible, could hardly 

 remain unnoticed and unexploited by 

 the ants in their interminable search for 

 liquid food. 



Some ants (Leptotlwra.r sp. ) obtain 

 the honey-dew merely by licking the 

 surface of the leaves and stems on which 

 it has fallen, but many species have 

 learned to stroke the aphids and induce 

 them to void the liquid gradually so that 

 it can be imbibed directly. A drove of 

 plant-lice, especially when it is stationed 

 on young and succulent leaves or twigs, 

 may produce enough honey-dew to feed 

 a whole colony of ants for a consider- 

 able period. But the aphidicolous habit 

 has not been acquired by all ants. 

 The highly carnivorous Dorylinre and 

 Ponerin?e never attend these insects and 

 care nothing for their excretions, and 

 the same is true of the exquisitely car- 

 nivorous, granivorous and fungus-eating 

 genera of Myrmicinae (Pseudomyrma, 

 Pogonoinynne.r, Atta, etc.). Other 

 Myrmicine genera, such as Myrnrica, 

 Cremastog aster, Tetramorinui and Mon- 

 contain many aphidicolous spe- 



aphid- 



FIG. 205. Carton 

 ,^"' by t 



olata on twig of swamp- 

 cies. The tWO highest subfamilies, how- huckleberry. (Original.) 



ever, the Dolichoderinx and Campono- 



tinse, represent the most perfect development of the habit, espe- 

 cially the genera Iridomyrmex, Dolichoderus, Azteca and Lioinc- 

 topwn of the former, and Lasius, Brachyinynnc.r, Prenolcpis, 

 Plagiolepis, CEcophylla, Formica, Mynnccocystiis and Lasius of the 

 latter subfamily. In our north temperate region the species of Lasius 



