426 N. E. MCINDOO. 



through the subcosta (Sc) while the largest nerves (TV) pass through 

 the veins bearing the olfactory pores. The nerve and trachea 

 run directly beneath the sense cells (SC) and from the nerve 

 pass off many branches which connect with the sense cells. In 

 the costa (C) and subcosta (Sc) where there are no sense cells, 

 only a few nerve fibers can be seen. 



In the preceding pages it has been shown that there are many 

 variations in the structure of the olfactory pores of beetles, and 

 that these organs are very similar to those of hymenopterous 

 insects. On the basis of the location of the pore apertures in 

 the integument, the olfactory organs in beetles are intermediate 

 between those of spiders and those of Hymenoptera. 



EXPERIMENTS TO DETERMINE THE LOCATION OF THE OLFACTORY 



ORGANS. 



Since it is now generally believed that the olfactory organs of 

 beetles are borne by their antennae, these appendages of many 

 individuals were pulled off. From one to seven days later, the 

 mutilated insects were tested with odors. In the preceding pages 

 it has been shown that the olfactory pores of Coleoptera are 

 located on the peduncles of the elytra, on the wings and on the 

 legs. In order to ascertain if these structures receive odor 

 stimuli, the elytra, wings and legs were mutilated. One or more 

 days later these mutilated beetles were tested with odors. In all 

 the experiments with unmutilated and mutilated beetles, 434 

 individuals have been tested. These belonged to 11 species 

 representing eight families. 



In order that the behavior of the mutilated beetles would be 

 correctly interpreted, the behavior of unmutilated beetles under 

 experimental conditions was first studied. Since it was not 

 desired to ascertain the relative sensitiveness of males and 

 females, both sexes were used indiscriminately. To determine 

 the relative sensitiveness of unmutilated and mutilated indi- 

 viduals under conditions which permitted of their close observa- 

 tion, triangular experimental cases were employed. These were 

 made of three narrow wooden strips, two of which were five and 

 the third four inches long, each strip being half an inch thick. 

 Wire screen served as a bottom and glass as a top for the case. 



