ANTS AND APHIDS 



361 



Fig. 227. — An example of a complex interrelationship of organisms. Three 

 large brown ants (Camponotus?) are guarding a small colony of aphids from 

 which they obtain honey-dew; the abdomens of these three ants being greatly 

 distended with what they obtained in this way. The day after the above sketch 

 was made the large ants had been driven away by a large band of small black 

 ants, which then took possession of the aphid colony. The aphids in this case 

 are feeding on a fungus (Peridermium?) which, in turn is parasitic in the bark 

 of the trunk of a pine tree. Ants are known to care for the eggs of aphids during 

 the winter, and carry the young to appropriate food plants, and then guard the 

 aphid colony from the attacks of other predatory insects. For this service the 

 aphids pay a tax in honey-dew. The honey-dew is a clear, sweet fluid secreted 

 in drops from the anus (not from the tubules on the dorsal surface of the abdo- 

 men). The ants stimulate the aphids by stroking them with their antennae; 

 to this the aphids respond by voiding a droplet of the honey-dew. 



