NO. 9 OLFACTORY SENSE OF INSECTS McTNDOO 37 



cuticular surface, beneath which the wall of the nervure is deficient, so as to 

 allow a free communication with its interior ; these organs are arranged in 

 rows on the halteres and in variously shaped groups in the wings. 



He examined one or more species of about two dozen genera 

 representing all of the insect orders. He observed these organs in 

 the honey bee, in Vespa, and in all other species examined by him 

 except Corysus [Corizus], the bedbug (Cimex lectularius), an apter- 

 ous beetle, and the flea (Pitlex hritans). Usually these structures 

 consist of two groups on the upper, and one scattered group on the 

 under side of the subcostal vein, amotmting in Opiiion to from 200 

 to 300 above, and perhaps 100 beneath, with a smaller group at the 

 end of the vein. In the Diptera these vesicles are found both on the 

 wings and halteres. In the Coleoptera they are highly developed and 

 occur in numerous groups on the subcostal vein, mostly at the widest 

 part, but are also scattered along it to the joint of the wing. In 

 Carabus (a beetle) they are found on veins other than the subcostal. 

 In many beetles the vesicle is overarched by a hair, which probably 

 protects the organ. He could distinguish no differences in the sexes 

 except that the vesicles were slightly larger in the females, due to 

 their greater size. These organs are most perfectly developed in the 

 Diptera, slightly less perfectly developed in the Coleoptera, rather 

 less so in the Lepidoptera, only slightly developed in the Neuroptera, 

 scarcely at all in the Orthoptera, and only a trace of them exists in 

 the Hemiptera. He gives several drawings, but they represent only 

 the superficial appearances. 



Hicks (i860) discovered these same vesicles on the trochanter 

 and femur, chiefly on the former, in all the insects he examined. In 

 Formica rufa (an ant) these structures are numerous and exist both 

 on the trochanter and femur. A few small groups of these vesicles 

 are also present on the proximal end of the tibia in this ant. In the 

 honey bee these organs are not so abundant on the legs but are located 

 at the same places as on the ant. The vesicles on the legs, like those 

 on the wings, consist of a thin, delicate membrane 



stretching over, and closing in from the air, a tubular aperture in the chitin- 

 layer of the part. This aperture may be circular or oval, the tube varying in 

 length according to the thickness of the integument, curved as in the Hornet, 

 or forming a globular cavity as in Silpha. The delicate membrane which 

 covers over this aperture is generally level, sometimes leaving a ridge or a 

 minute papilla in its center. 



Hicks gives drawings showing the disposition of these vesicles or 

 pores on the wings and legs of many of the species examined. He 

 saw nerves running to all of these organs and gives a very good idea 



