II FOOD OF INSECTS 65 



ing. This agency is assisted in great measure by the 

 lateral canals, or tracheal vessels of the organ. The 

 butterfly at the instant that it alights upon a flower 

 makes a forcible expiratory effort, by which the air is 

 removed both from the tracheae of the proboscis and 

 from those with which they are connected in the head, 

 and at the moment of applying its proboscis to the 

 food it makes an inspiratory effort, dilating the tube, 

 and the food is carried along it quickly to the mouth 

 to supply the vacuum produced, without any inter- 

 ruption of the function of respiration. By this com- 

 bined agency of respiration and muscular action, we 

 can understand how a butterfly is enabled to extract 

 in a moment the honey from a flower while hovering 

 over it. This it certainly would be unable to do so 

 rapidly, were the ascent of the fluid dependent on the 

 action of the muscles of the proboscis alone. 1 



Vegetable-feeding insects have little or no difficulty 

 in procuring food. All nature lies before them, and 

 unerring instinct is a guide that never fails or falters 

 in directing them, by flight or foot, to the substance 

 constituting their proper aliment. It is only under 

 extraordinary circumstances, in face of the unwonted 

 destruction of plants or when the numbers of these 

 tribes are unusually increased, that they ever perish 

 from starvation. The carnivorous species experience 

 a harder struggle for existence. They are exposed to 

 the dangers of deficiency and deprivation, but fortun- 

 ately they are frequently endowed with the faculty of 

 enduring long abstinence. The kind of food they take 

 leads them to employ a variety of methods in supply- 



1 Newport. 



F 



