44 N. E. McINDOO 



wings, mouth parts, and the total number of pores on each of the 

 43 specimens examined. In the preceding pages the insects are 

 usually referred to in this table by their respective numbers. 

 The blank spaces in the fourth column mean that the mouth 

 parts were either missing or so badly mutilated that the pores 

 on them could not be counted. Owing to the rudimentary con- 

 dition of the mouth parts, no attempt was made to identify 

 accurately the various mouth appendages, but most of the pores 

 recorded were found on the bases of the palpi, as is best illus- 

 trated in the lesser wax moth (no. 22). The only pores found on 

 the mouth parts of Euvanessa antiopa and Papilio polyxenes 

 (nos. 31 and 41) lie in two groups at the base of the proboscis, 

 on the dorsal surface, in the same position as recently stated for 

 the honey bee by the writer ('16). 



Structure 



The preceding pages deal with the disposition of the olfactory 

 pores, and a discussion of the anatomy of these organs is given 

 in the following pages. 



a. External structure. When the superficial ends of the olfac- 

 tory pores are examined under a high-power lens with a strong 

 transmitted light, the pores appear as small bright spots, each 

 of which is surrounded by darker chitin, the pore border (fig. 

 4 E, PorB) and by the pore wall (PorW). The pore aperture 

 (PorAp) is usually oblong, but may be round; its size depends 

 upon the focusing level of the microscope, showing that it is 

 funnel-shaped. The size of the pores vary considerably, as may 

 be seen by referring to figure 4. 



b. Internal structure. The olfactory pores have been called 

 dome-shaped organs, but the domes are not always present as is 

 shown in figures 5 C and 8 C; in those sections in which the 

 domes are not visible the microtome knife probably passed 

 through the organ too far from the pore aperture. The domes 

 (fig. 5 B and D, D) in the wings and legs of moths, and in the 

 wings (fig. 9 A) of a butterfly rise slightly above the surface of 

 the surrounding chitin, while in the legs of the same butterfly 



