52 N. E. McINDOO 



It is thus seen that in Lepidoptera pore plates, common to 

 most insects, are entirely absent, while the pegs are practically 

 wanting; however the pegs seem to be replaced by the end pegs. 

 Of the five sense organs on the antennae of Lepidoptera, only the 

 pit pegs and end pegs are regarded as olfactory organs. Since 

 the end pegs are totally absent in Psyche and Ino, it does not 

 seem reasonable that they can be olfactory organs for any 

 lepidopteron, and, providing, there is no sexual difference in the 

 size of the pit pegs, the male of Fidonia smells three and one- 

 half times as well as the female of the same species; the male of 

 Orgyia eight times as well as the female of that species, and while 

 the male of Psyche smells well, the female of the same species 

 can not smell at all. It also seems doubtful that the pit pegs can 

 function as olfactory organs. 



Now let us inquire if any of these organs are really adapted 

 anatomically to receive olfactory stimuli. 



Structure 



The ventral side of the shaft (fig. 10 A) of the antenna of 

 Fidonia bears more sense organs than does the dorsal side, and 

 the terminal segment bears more pit pegs (PPg) than does any 

 other segment. Observed from the side under a high-power 

 lens, the pit pegs look like pits lined with hairs, but when viewed 

 from the tops of the pits, the organs resemble small wheels in 

 that the hairs form the spokes and the base of the peg the hub. 

 Two of the pit pegs thus viewed are shown on the segment third 

 from the last one. , 



A longitudinal section of a pit peg shows that a peg (fig. 10 B, 

 PPg), surrounded by a crown of pseudo-hairs (Hr^), arises from 

 the bottom of the pit and that the base of the peg is connected 

 with a sense cell group (SCG). The end pegs (fig. 10 C, E Pg) 

 are nothing more than short, stubby hairs supported on stout 

 projections, called styles (St), which are innervated. The 

 bristle-like hairs (fig. 10 D), ordinary hairs (fig. 10 E, Hr) and 

 pegs are also innervated. 



Other authors who have studied the anatomj^ of these organs 

 describe them as similarly to the preceding account, except the 



