248 



COLLEGE ZOOLOGY 



Antennae 



The antennae of insects are usually tactile, 

 auditory, or olfactory in function. Interest- 

 ing experiments by von Frisch have led him 

 to the conclusion that bees can select certain 



odors; for example, they can select an odor 

 derived from orange peel from among 43 

 others. He has also demonstrated that bees 

 can find feeding places through a sense of 

 smell. Experiments based on the removal of 

 antennae indicate that the olfactory sense 



Figure 147. Antenna of Coleoptera showing variations within a single order of insects. A, 

 Elateridae, click beetle. B, Lampyridae, firefly. C, Gyrinidae, whirligig beetle. D, Silphidac, 

 Necrophorm, burying beetle. E, Curcuhonidae, weevil. F, Scarabaeidae, lamellicorn beetle. All 

 highly magnified. 



organs are located on this structure. Anten- 

 nae differ in form and structure (Fig. 147), 

 and often the antennae of the male differ 

 from those of the female. 



Digestive tract 



Of the internal organs of insects, the 

 digestive tract and respiratory system are of 



particular interest. The digestive tract is 

 modified according to the character of the 

 food; that of the grasshopper is typical of 

 vegetable-eating insects. Suctorial insects, 

 like the butterflies and moths, are provided 

 with a muscular pharynx which acts as a 

 pumping organ, and a crop for the storage 

 of juices. 



Esophagus 



Rectum 

 Anus 



Labial pa 



Cecum 

 intestine 



Maxillae fused to form proboscis Malpighian tubule 



Figure 148. Digestive tract of a sucking insect. Diagram of the internal organs from the 

 left side. 



