ANTS 169 



claim that many plants not only offer special inducements 

 to attract ants to them by affording favorable nesting 

 places, but also offer the ants delectable food in the way 

 of a sweet liquid, the floral and extrafloral nectar. In 

 return for the domiciles and the food, the ants are sup- 

 posed to protect their plant hosts from certain insect and 

 other animal enemies. In other words, the relationship 

 is one of mutual benefit or a symbiotic one. It is cer- 

 tainly true that many species of ants make their homes 

 in the hollow stems of plants, in the thorns of acacias 

 which the ants easily hollow out, in cavities in bulbs, 

 leaves, and in the dried seed-pods of plants. It is also 

 true that ants assiduously collect and carry to their nests 

 the sweet nectar excreted by many plants. It is not so 

 clear, however, that these favorable nesting places and 

 the nectar are provided by the plants on purpose to attract 

 the ants, nor is it clear that the ants afford the plants 

 protection from the animal enemies. In other words, 

 more definite proof is needed to show that the relations 

 between ants and plants is a purposely mutual one. 



On the other hand, the relation of ants to plant-lice, 

 tree-hoppers, and certain scale insects is clearly, in many 

 cases, a mutually helpful one. Especially is this true of 

 the relations between ants and plant-lice. The aphids 

 secrete a sweet liquid known as honey-dew, of which 

 the ants are very fond and which they are active in 

 collecting and carrying to their nests. It can hardly be 

 supposed that the aphids excrete the honey-dew solely 

 for the ants. The liquid is an excretion from the ali- 

 mentary canal and is exuded whether ants are in attend- 

 ance or not. On the other hand, ants are very solicitous 

 in their care of aphids in return for the honey-dew. The 



