ENTOMOLOGY 



In aquatic insects,, indeed, the senses of taste and smell are not differen- 

 tiated, these forms having 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 inconceivably acute. Hosts of insects depend chiefly 

 on their olfactory powers to find food, for example many beetles, the flesh 

 flies and the flower- visiting moths; or else to discover the opposite sex, 

 as is notably the case in saturniid moths. In dragon flies, however, this 

 sense is relied upon far less than that of sight. 



Organs of Smell. By means of simple but conclusive experiments, 



Hauser and others have shown that 

 the antennae are frequently olfactory 

 though not to the exclusion of tac- 

 tile or auditory functions, of course. 

 Hauser found that ants, wasps, vari- 

 ous flies, moths, beetles and larvae, 

 which react violently toward the vapor 

 of turpentine, acetic acid and other 



tk 



tc.... 



FIG. 128. Under side of left maxilla FIG. 129. Longitudinal section of gustatory 

 of wasp, Vespa vulgaris. p, palpus; pr, end-organ (tc, of Fig. 128). c, cuticula; h, hypo- 

 protecting hairs; tc, taste cup; th, tactile dermis; sc, sensory cell; tc, taste cup. After WILL. 

 hair. After WILL. 



pungent fluids, no longer respond to the same stimuli after their antennae 

 have been amputated or else covered with parafiine to exclude the air. 

 His experiments were conducted under conditions such that the results 

 could not be ascribed to the shock of the operation or to effects upon the 

 gustatory or respiratory systems; except for having lost the sense of 

 smell, the insects experimented upon behaved in a normal manner. It 

 should be said, however, that Carabus, Melolontha and Silpha still re- 

 acted to some extent toward strong vapors even after the extirpation of 

 the antennae; while in Hemiptera the loss of the antennae did not lessen 

 the response to the odors used. These facts indicate that the sense of 



