NO. 9 OLl-'ACTORV SENSE OE INSECTS McIXDOO 39 



thill chitin is arched in the shape of a dome. Each his^ht spot is sur- 

 rounded by a dark, chitinous rinp^.- The internal anatomy consists 

 of a sense cell, sense fiber, and a Hasklike cavity with its chitinous 

 cone. All of these parts are almost identical to those in Hymenoptera 

 described by the author but ( iuenther failed to see the sense fiber join 

 the aperture at the bottom of the flask. Thus his drawinj^ shows a 

 thin chitinous arch or dome which completely closes the external end 

 of the flask, the sense fiber running; up against this chitinous dome. 

 If he had prepared more sections and used li_oht colored stains such 

 as safrain and not dark stains like hamatoxylins. he could certainly 

 have seen the sense fiber join the aperture in the dome. Guenther 

 tries to liken these pores to the membrane canals of \'om Rath. A 

 similar dome-shaped membrane was found in the antennae of lamelli- 

 corn beetles by Hauser, Krapelin. \*om Rath, and others, but these 

 bear a little hair at their center. Hauser attributes an olfactory 

 function to such structures, but Guenther shares the opinion with 

 \'om Rath and Graber that they have an auditory role. 



Janet (1904) found porelike sense organs in large numbers in all 

 the ants that he examined. These pores are either widely separated 

 or, more frequently, united into groups. They occur on the labial 

 palpi and on the tongue, and there are some on the pharynx, besides 

 many on the legs. Janet recognizes those on the legs as the same 

 vesicles or organs that Hicks describes in i860. In a wasp fJ^espa) 

 and an ant (Formica) their disposition is almost identical with that 

 in the honey bee. Janet's drawings of the superficial aspects of these 

 pores are very similar to those of the author but on account of the 

 small size of the specimens he seems to have had trouble in under- 

 standing their internal anatomy. According to him, all the pores, 

 whether on the mouth parts or legs, have a similar structure, and they 

 resemble the structure of the olfactory pores found in the honey bee ; 

 however, there are a few slight differences. He calls the chitinous 

 cone an umbel, which is always separated from the surrounding 

 chitin by a chamber. This chamber communicates with the exterior 

 by means of the pore. The sense fiber, or his manubrium, runs into 

 the umbel, and he thinks that it spreads out over the inner surface 

 of the umbel and does not open into the chamber. Thus the umbel 

 forms a thin layer of chitin which separates the end of the sense fiber 

 from the external air. The role of these organs is evidently to permit 

 the end of the nerve to become distributed on a surface relatively 

 large and separated from the air only by a thin layer of permeable 

 chitin. Janet fails to give drawings that show the sense fibers run- 



