26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



by emitting odors. Since odors from the steam distillates and emana- 

 tions from 4 or 5 species belonging to the potato family attracted 

 potato beetles, it was then suggested that the chemist tell us what 

 constituent or constituents, common to these plants, did the attracting. 

 If we had this information, we might be able to use these substances 

 in poison baits. 



(e) repellents used against beetles 



Under this heading many repulsive substances are regarded as 

 repellents, but for some of them a more appropriate word would be 

 deterrents; nevertheless, there is little distinction between these two 

 words. Let us define a repellent as an odorous substance, which by 

 means of its unpleasant exhalations repels insects before they have 

 touched it ; and a deterrent as an inodorous substance which repels 

 insects after they have touched it. Thus defined, a deterrent repels 

 mostly, if not entirely, through the sense of touch; while a repellent 

 operates either through the sense of smell or, if its exhalations are 

 poisonous, then through the breathing pores. These definitions are 

 easily made, but it is j^erhaps almost impossible to have a deterrent 

 which is totally inodorous to insects ; and furthermore, other factors 

 are often involved. These terms have been used loosely by various 

 writers, and since this subject is yet confused, the present writer will 

 still continue to use them without attempting to explain how the 

 enumerated substances repel, deter, or otherwise keep insects away 

 from plants. The following remarks by the writer's reviewers help 

 to elucidate the subject. 



In regard to the Japanese beetle. Doctor Van der Meulen and Mr. 

 Van Leeuwen believe that there should be another subdivision of 

 repellents to include those substances which mask attractive odors ; 

 for example, those from geraniol. We might call these " maskers " or 

 " neutralizers," because they repel from a short distance merely by 

 covering up or neutralizing the attractive odors. Relative to " in- 

 odorous " materials, Japanese beetles may also be repelled before 

 touching dusted or sprayed food by means of the sense of sight. In 

 regard to the repellency of the arsenates, the subject of toxicity should 

 also be considered ; but at present we are not able to evaluate the 

 various factors, including the senses of sight, smell, touch, taste, and 

 probably a general sense connected with the digestive system. 



After reading the preceding definitions. Dr. F. L. Campbell pro- 

 posed that attrahents, now usually called attractants, should be di- 

 vided. The odor from geraniol causes the Japanese beetle to orient 

 and to move toward this substance ; therefore, geraniol is a true 





