2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



PAGE 



(8) Water extract and steam distillate of bean leaves tested. 41 



(9) Chemotaxis more important than phototaxis in the find- 



ing of food 42 



(10) Repellents would probably not protect beans 42 



III. Thermotaxis 43 



I. Review of literature 43 



B. Sensory receptors 43 



I. Photoreceptors 44 



II. Chemoreceptors 44 



1. So-called olfactory organs 44 



(a) Antenna! organs 44 



(b) Olfactory pores 45 



2. So-called taste organs 54 



III. Audireceptors 56 



1. Johnston organs 56 



2. Chordotonal organs 56 



IV. Thigmoreceptors 57 



I . Tactile hairs 57 



C. Scent-producing organs and reflex " bleeding " 58 



Summary 61 



Literature cited 64 



Introduction 



This paper is a continuation of a series of studies dealing with 

 the tropisms and sense organs of insects, suggested by Dr. A. L. 

 Quaintance, Associate Chief of the Bureau of Entomology. It is 

 written as a complement to the writer's former paper (47) entitled 

 " Tropisms and Sense Organs of Lepidoptera," and contains practi- 

 cally no information found in the former one, although, of course, 

 the information which deals with the Coleoptera alone, is of a similar 

 nature. 



In the paper on Lepidoptera the original work dealt mostly with 

 the codling moth, but since this species was not a favorable insect on 

 which to experiment in the laboratory, the original plan for conducting 

 tests was much curtailed. In the present study the experimental work 

 has been expanded and the Mexican bean beetle (Epilachim corrupta 

 Muls.), which first appeared in Takoma Park and Sligo, Md., in 

 1927, was selected to represent the Coleoptera, owing to its abundance 

 and great economic importance. When tested to odor stimuli alone 

 it also was found to be an unfavorable insect ; but when the adults 

 were allowed to come in contact with the substances to be tested as 

 foods, the beetles clearly demonstrated their likes and dislikes ; and 

 when tested to light and gravity in a dark-room, the adults proved to be 

 almost ideal for this purpose. 



