6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 63 



GLANDS OF HEAD AND THORAX AS SEAT OF OLFACTORY 



ORGANS 



Ramdohr (1811) states that many species of insects, and among 

 them the bee, have a well-marked sense of smell. He failed to find 

 olfactory organs in the spiracles, but conceived the idea that odors 

 come into the mouth through the lumen of the proboscis. He found 

 behind the mouth a tube which is divided into three branches, the 

 smallest of which runs along the cesophagus above the first thoracic 

 ganglion and soon divides into two smaller tubes which pass into the 

 thorax and seem to connect with the large trachea coming from the 

 first spiracle. The other two branches pass at right angles into the 

 sides of the head, where they expand into four small sacs which 

 differ from air tubes in having walls that are soft, thick and trans- 

 parent. A thick tissue of the finest tracheae covers these various 

 tubes. Ramdohr also mentioned nerves running to his supposedly 

 olfactory organ. He was led to believe that air carrying odors passes 

 through the lumen of the proboscis into these small sacs and, as their 

 walls are soft and perforated with minute air tubules, that they act as 

 an organ of smell. Referring to Snodgrass ( 1910) and judging from 

 the foregoing description, Ramdohr probably mistook the thoracic 

 salivary gland for the branch accompanying the oesophagus, and the 

 salivary glands in the posterior part of the head for the other two 

 branches. 



CESOPHAGUS AS SEAT OF OLFACTORY ORGANS 



Treviranus ( 1816) infers that the smelling organs in various fami- 

 lies of insects are located in the throat. In all the insects discussed 

 the oesophagus is dilated, as in the bee, in front of the stomach into 

 a large sac-like reservoir, which he thought is perhaps for the purpose 

 of drawing air into the throat. He believed that in the presence of 

 strong-smelling substances the antennre do not produce noticeable 

 movements. He further stated that the olfactory apparatus of higher 

 animals and the antennae and palpi of insects are as different in 

 structure as organs can ever be. In order to smell, higher animals 

 must inhale the odoriferous particles. On the contrary, the antennae 

 and palpi do not conform with this general rule; in most insects 

 these appendages are not coated with a mucous skin and the interior 

 is carefully guarded against the entrance of odoriferous air. Tre- 

 viranus therefore infers that the sac-like reservoir " honey stomach " 

 in the bee, is for the purpose of drawing odorous air into the 

 cesophagus. 



