NO. 9 OLFACTORY SENSE OF INSECTS McINDOO 21 



Gum on the antennae did not prove satisfactory for abolishing sense 

 of odors, nor could they be burnt off without considerable injury to the 

 fly. He etherized some flies and cut the joint off with fine scissors 

 and declares that the ether did not affect the results of the experi- 

 ments with odors. 



It, therefore, seems certain that the sense of smell is absent, or at least 

 greatly reduced in flies that have lost the terminal joints of the antennae. 



He thinks that these flies when normal find their food wholly by 

 smell. 



When one antenna is lost and the other antenna is stimulated by food odor, 

 circus movements are carried out in . such a way as to prove that the fly 

 orients normally by an unequal stimulation on the antennae. 



Kellogg (1907) informs us that the female silkworm moth pro- 

 trudes a paired scent organ from the hindmost abdominal segment. A 

 male moth with antennae intact and with eyes blackened finds a female 

 immediately and with just as much precision as when his eyes are 

 not blackened. A male with the antennae extirpated and eyes not 

 blackened does not find the female unless by accident. Males with 

 antennae intact become greatly excited when a female is brought 

 within several inches of them. If the excised scent glands are laid 

 near the female from which they were taken, the males always neglect 

 the near-by live female and go directly to the scent glands and try 

 to copulate with them. A male with its left antenna removed, when 

 within 3 or 4 inches of a female with protruded scent glands, becomes 

 greatly excited and moves in circles around her to the right. A male 

 with right antenna off circles to the left. 



Sherman (1909) discusses the sense of smell in insects without 

 even giving any references or without performing any experiments. 



He says: "The organs of smell are the antennae." Insects that 

 feed upon decaying matter find their food almost entirely by smell. 

 When their antennae are removed they are unable to find their food 

 even though it is quite near and in full view. " This indicates that 

 the sense of sight is defective and that of smell very acute." 



To ascertain if the antennae of honey bees, ants and hornets carry 

 the olfactory organs, the author performed the following experi- 

 ments. Worker bees with one antenna pulled off are much less pug- 

 nacious than are those with the antennae intact, and they " pay less 

 attention " to each other. They appear otherwise normal, except that 

 their ability to communicate is considerably decreased. In observa- 

 tion cases they live only 6^ days while workers with unmutilated 

 antennae live 9^ days under the same conditions. When tested 

 with the three essential oils — peppermint, thyme and wintergreen — 



