STRUCTURE AXD CLASSIFICATION. 



peared entirely, and all the other structures have been so modi- 

 fied that nothing remains except this flexible sucking tube. I 

 use the term "tube," although it is not such in reality, being 

 made up of two hollow crescents, more or less firmly held to- 

 gether, so that, practically, it serves all the purposes of a complete 

 tube. When the insect feeds the tongue is extended, the muscu- 

 lar structure being accommodated in the walls of each half of the 

 tube. Fig. 4 illustrates a section through a butterfly tongue, 

 showing the way in 

 which the two parts 

 are united. At its 

 tip there are often 

 more or less devel- 

 oped processes which 

 serve as taste cups, 

 and also to assist in 

 gathering up the 

 minute globules of 

 nectar. 



A tongue of this 

 description indicates a type which can never be harmful to vege- 

 tation, because it is not fitted for either piercing or eating plant 

 tissue ; but it is, on the contrary, of direct use in pollenizing 

 flowers. Butterflies and moths are never injurious in the adult 

 stage, however much their larvae may offend ; but many are 

 especially adapted for pollenizing certain flowers. Thus the 

 " Hawk-moths," with tongues five and six inches in length, are 

 able to reach to the very base of flowers like the petunias, even- 

 ing primrose, " Jimpson weed," and many orchids. 



A widely different type of sucking mouth is found among the 

 "bugs," or Heiniptera. Here, instead of a flexible tube, there 

 is a jointed, rigid beak or rostrum, made up of either three or 

 four segments, inside of which run four pointed lancets. This 

 beak is not a complete tube, but narrowly open in front and at 

 the tip, to permit the protrusion of the lancets. Insects with this 

 structure gain their food by piercing the plant tissue and sucking 

 the juices, and such a structure always leaves its possessor open 

 to the suspicion of being injurious. As a matter of fact, many of 

 the Hemiptera are really predaceous upon other insects ; but, as 



Fig. 4. 



Section through a butterfly tongue. 



