THE OLFACTORY SENSE OF COLEOPTERA. 449 



the pore aperture and cone, and it enters the bottom of the pore 

 aperture or pit where its peripheral end comes into direct contact 

 with the outside air. In Hymenoptera the sense fibers enter the 

 pore apertures which are almost on a level with the external 

 surface of the chitin. In Coleoptera, with a few exceptions, the 

 sense fibers enter the bottoms of pits which lie in the chitin one 

 third (at time of emerging into imago stage) the distance from 

 the external surface. In the legs of the lady beetle, Epilachna 

 borealis, instead of the chitin which surrounds the pore apertures 

 being depressed, it is elevated so that the pore apertures He in 

 the center of domes above the general surface of the legs. In 

 the legs of the blister beetles, Epicauta marginata and E. penn- 

 sylvanica, the pore apertures lie on a level with the surface of 

 the legs. In the legs of the potato beetle, the pore apertures lie 

 at the bottoms of shallow pits. All four preceding species have 

 hypodermal gland pores over the entire body, except the wings. 

 These pores in the lady beetle are perhaps the most highly 

 developed. They lie on all sides and even among the olfactory 

 pores on the legs. In the other three species they are less highly 

 developed on the legs near the olfactory pores and none is found 

 very close to an olfactory pore. This correlation between the 

 hypodermal gland pores and the olfactory pores is certainly a 

 means of preventing the secretion from the gland cells from 

 running into the pore apertures. 



A large nerve and a large trachea run into each elytron and 

 wing. In the peduncle of the elytron they run through the 

 radial plate just beneath the group of olfactory pores. Branches 

 from the nerve are given off which connect with the sense cells. 

 The large nerve and trachea passing into the wing soon divide 

 so that a smaller nerve and a smaller trachea run through each 

 main nerve. The largest trachea passes through the subcosta, 

 and the largest nerves pass through the veins carrying the ol- 

 factory pores. These nerves give off branches which connect 

 with the sense cells. The sense cells wherever found are always 

 surrounded by blood. 



In the experiments to determine the location of the olfactory 

 organs, 434 individuals were tested. These belonged to ii 

 species representing 8 famihes. After the antennse were pulled 



