9 8 



ENTOMOLOGY 



FIG. 128. 



tc 



>tk 



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- 

 moths ; or ^ to discover 



protecting hairs; tc, taste cup; th, the Opposite SCX, 3S is llOtably 

 tactile hair. After WILL. , . ... 



the case in satumnd moths. 

 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 

 functions, of course. Hauser 



found that antS, WaSpS, Vari- ula ; h > hypodermis; sc, sensory cell; 

 n . tc, taste cup. After WILL. 



ous flies, moths, beetles and 



larvae, which react violently toward the vapor of turpen- 



Longitudinal section of gustatory 

 end-organ (tc, of Fig. 128). c, cutic- 



