1921] Scent glands of CoJeoptem 145 



?^^OTES OX DEFENSIVE SCEXT GLAXDS OF CEBTAIX 



COLEOFTEEA. 



By J. S. Wade, 



Scientific Assistant, Bureau of Entomology. 

 Washington, D. C, 



The attention of the writer was first directed to the functions 

 of defensive or repugnatorial scent glands in certain Coleoptera 

 during the study some time ago of the biology of some of the more 

 common species of Coleoptera belonging to the Tenebrionid tribe 

 Eleodini, inhabiting portions of the central Great Plains region. 

 Later, a growing interest led to closer field observation and to the 

 examination, as opportunity offered, of available literature on the 

 subject. The notes which follow are intended merely to supple- 

 ment data already published, to which reference is made. 



It is obvious to anyone at all familiar with insect life, that the 

 degree of sensitiveness and response in insects to certain external 

 phenomena is enormously greater than in vertebrates, and that 

 their organs of sense are developed accordingly. It always has 

 been a cause for wonder to hiunan beings as to the means by which 

 the various lower animals recognize, distinguish and communicate 

 with each other. Although we know very little about the senses of 

 the lower animals, it long has been knovm that such senses as 

 sight or touch are not nearly so important to insects as to us. 

 We know that insects actually do distinguish and communicate with 

 each other, or are attracted or repelled by each other, and as the 

 means of communication are not known to use, may we not safely 

 assume that such is brought about through factors, the existence 

 of which is not yet recognized or understood? Packard (1898) 

 has called attention to the ease and rapidity with which exceed- 

 ingly delicate, attenuated, and highly volatile odors unlaiown to us 

 are perceptible to insects. Mclndoo (1917) has suggested the 

 presence of a chemical sense or senses, somewhat comparable to our 

 olfactory sense, which receives and transmits stimuli in a w'ay 

 somewhat like that of odors, and has ably discussed the results of 

 observations and experiments upon certain insects, and has given 

 a short historical review of the literature on the subject. In fact, 



