34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 63 



insect flies, the end rods serving such a purpose while the insect is 

 resting ; in Diptera the pit pegs, similar to those of hutterflies, are the 

 olfactory organs. Nagel repeated most of Hauser's experiments and 

 seems to be convinced that the antemije are almost always, if not 

 always, the seat of the organs of olfaction. When one or more of 

 these organs are absent the next best, histologically considered, must 

 perform the olfactory work ; and when all the antennal organs are 

 wanting, as in Ephemera I'lilgata, a pseudoneuropteron, he imagines 

 that the insect cannot smell. 



Dahlgren and Kepner ( 1908) regard the knob-shaped, pitlike an- 

 tennal organs of Necrophonis as the olfactory organs. They found 

 glandlike cells beneath the hypodermis which they believe to be asso- 

 ciated with these pits and perhaps aid in receiving odor stimuli. 



Nearly all of the foregoing observers have overlooked the sense 

 organ found in the second antennal joint of insects. This is called 

 Johnston's organ. In Vespa the upper end, or the nerve rod, of the 

 organ penetrates the articulating chitin between the second and third 

 joints and comes to the surface. PVom its structure an olfactory 

 sense might be attributed to it. According to Child ( 1894a and b), 

 who experimented extensively with mosquitoes, this organ serves as 

 a combined touch and auditory apparatus and has nothing to do with 

 olfaction. 



Lubbock (1899) says: 



Forel and I have shown that in the bee the sense of smell is by no means 

 very highly developed. Yet their antenna is one of those most highly organized. 

 It possesses — besides 200 cones [pegs], which may probably serve for smell — ■ 

 as many as 20,000 pits [pore plates] ; and it would certainly seem unlikely that 

 an organization so exceptionally rich should solely serve for a sense so slightly 

 developed. 



From this fact and his numerous experiments Lubbock regards the 

 antennas as the seat of the organs of olfaction, yet he does not commit 

 himself as to the particular antennal organs which receive the odor 

 stimuli. 



Burner (1902) states that only a few of the hair structures on the 

 antennse of Collembola may be regarded as olfactory organs. 



Schenk (1903) claims that the fact that the males of Apid?e (bees) 

 do not possess any pegs does not argue against the view that these 

 structures are olfactory organs for (i) the pit pegs, which certainly 

 have an olfactory function, are common to the antennre of males, 

 queens and workers, and (2) in hunting for the females the olfactory 

 sense appears to be of second place to sight. In the summary of his 

 observations on Lepidoptera Schenk asserts that the pit pegs function 



