208 A BOOK OF INSECTS 



protect their host-trees in return for the food and shelter 

 which they receive would be to endow these insects with 

 a power of reasoning which assuredly they do not possess. 

 In Java, there are some curious epiphytic plants which 

 produce large bulb-like excrescences, the chambers of 

 which are usually tenanted by ants ; but these swellings 

 are really water-reservoirs, and are not primarily con- 

 nected with insects. Nevertheless, the ants rush forth 

 when disturbed, and there is some reason for thinking 

 that the plant may derive benefit from their presence. 

 That ants guard and protect certain flowers is a well- 

 established fact, commented upon by Kerner. The young 

 flower- heads, or capitula, of certain thistle-like plants 

 indigenous to southern Europe are particularly liable to 

 the attacks of beetles, which bite big holes in the heads, 

 and thus work much injury. " Honey is secreted from 

 big stomata on the imbricating scales of the still-closed 

 capitula in such quantities that one can see a drop of it on 

 every scale in the early morning, whilst later in the day, 

 as the water evaporates, little masses, or even crystals, of 

 sugar are to be found. This sugar, either in its liquid or 

 solid form, is very palatable to the ants, which habitually 

 resort to these capitula during the period of its secretion. 

 And to preserve it for themselves they resent any invasion 

 from outside. If one of the beetles appears they assume 

 a menacing attitude. They hold on to the involucral 

 scales with their last pair of legs and present their fore-legs, 

 abdomen, and powerful jaws to the enemy. Thus they 

 remain till the beetle withdraws, if necessary hastening 

 its retreat by squirting formic acid in its direction. Then 

 they quietly begin to feed on the honey again. . . . As 

 soon as the florets on the heads begin to open, the secre- 

 tion of honey diminishes and ultimately ceases. No longer 

 do beetles come to devour them, nor is there any further 



