ENTOMOLOGY 



FIG. 128. 



tc-,,. 



each seated in a pit, or cup, and connected with a nerve fiber 

 (Figs. 129, 130). In some cases, however, it is difficult to 



decide whether a given organ 

 is gustatory or olfactory, owing 

 to the similarity between these 

 -^ two kinds of structures. In 

 aquatic insects, indeed, the 

 senses of taste and smell are not 

 differentiated, these forms hav- 

 ing with other of the lower 

 animals simply a " chemical " 

 sense. 



Smell. In most insects the 

 sense of smell is highly efficient 

 and in many species it is incon- 

 ceivably acute. Hosts of in- 

 sects depend chiefly on their 

 olfactory powers to find food, 

 for example many beetles, the 

 flesh flies and the flower-visit- 

 ing moths; or else to discover 



protecting hairs; tc, taste cup; th, the Opposite SCX, as IS notably 



the case in saturniid moths. 

 FIG. 129. 

 U 



tactile hair. After WILL. 



In dragon flies, however, this 

 sense is relied upon far less 

 than that of sight. 



Organs of Smell. By 

 means of simple but conclu- 

 sive experiments, Hauser and 

 others have shown that the 

 antennae are frequently olfac- 

 tory though not to the ex- 

 clusion of tactile or auditory 



... f -f-r j>()iitiiiuuin,u SCULIUII ui 



functions, of course. Hauser end . organ (tc> of Fig . I28) . 



found that antS, WaSpS, Vari- 



ous flies, moths, beetles and 



larvae, which react violently toward the vapor of turpen- 



Longitudinal section of gustatory 

 c, cutic- 



ula; h, hypodermis; sc, sensory cell; 

 tc, taste cup. After WILL. 



