ELEMENTARY ENTOMOLOGY 



FIG. 49. Sensory cells 



in antennae of aphides. 



(Greatly magnified) 



Smell. Most insects depend upon their sense of smell to find 



their food and to discover the opposite sex. Thus beetles and flies 



are drawn to carrion and to decaying vegetation, 

 and in almost all cases it seems probable that 

 the food plant of an insect is distinguished by 

 smell rather than by sight. A confined female 

 Cecropia moth will often draw numerous males 

 from a considerable distance. Experiments 

 have shown that the antennae are the chief 

 organs of smell, though the maxillary palpi 

 and cerci detect certain 

 odors and enable certain 

 insects to smell when the 

 antennas are removed. 

 The olfactory function 

 of the antennae can be 



very easily shown by taking an insect which 



is definitely attracted to some substance by 



smell and removing the antennae or covering 



them with shellac, when 

 it will be found wholly 

 indifferent to what was 

 previously so attractive. 

 Vile-smelling substances FIG " SO Antenna of la- 



which are Supposed to mellicorn beetle 



repel insects are USUally Showing smelling pits on the 



of no vail IP not afferf expanded terminal segments. 

 e > (After Jordan and Kellogg) 



ing the insect as they do 



man. Some attempts have been made to utilize 

 the sense of smell in luring insects to destruc- 

 tion, but as yet with no very marked success, 

 though there is promise of possible control of 

 some pests in this way. 



Hearing. There is no evidence that hearing 

 is generally developed in insects, but in many 

 groups we naturally infer its presence from the 

 fact that characteristic noises are produced, as the ' singing ' of 

 the cicada and katydid. These noises are produced in various 



FIG. 51. Under sur- 

 face of right wing 

 of the male cricket. 

 (Enlarged) 



/, rasp ; 2, position of 

 scraper, only scraper of 

 the left wing used; j, 

 attachment of wing. (Af- 

 ter Linville and Kelly) 



