34 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8l 



Cabbage butterflies (Pontia (Picris) rapco L.) were confined by 

 Minnich (63) in an odor chamber (fig. 11, A). Since they are fond 

 of apple juice its odor was used to stimulate the smelling organs, and 

 the responses to it were then measured by the extent to which the 

 proboscis was uncoiled for the purpose of partaking of the apple 

 juice, although the insects could not reach it. The antennae were 

 mutilated in three ways: (i) Covered with vaseline; (2) covered 

 with a mixture of paraffin and vaseline; and (3) cut ofif at the base 

 with fine scissors. When the organs on only one antenna were pre- 

 vented from functioning, the olfactory response was reduced only 

 6 per cent ; when those on both antennae were eliminated or prevented 

 from functioning, the response was reduced 58 per cent. Thus accord- 

 ing to these results nearly half of the olfactory receptors must be 

 located elsewhere than on the antennae. In his own words Minnich 

 (P- 354) says: 



After the antennae are eliminated the animals were still 42 per cent responsive. 

 Considering the variety of methods employed and the similarity of results ob- 

 tained, this figure is much too large to be attributed to a failure to eliminate the 

 antehnal organs completely. It must, therefore, mean that there are olfactory or- 

 gans on other parts of the body as well as on the antennae. ... I cannot, there- 

 fore, concur with Mclndoo in the view tliat the antennae of adult insects in gen- 

 eral lack olfactory organs. Certainly, such is not the case with Pieris. Nor can 

 I agree with the opposing viewpoint, that the olfactory organs of adult insects 

 in general are confined to the antennae. In this respect the results on Pieris 

 differ from those obtained by v. Frisch in his ingenious experiments on bees. 

 The results of the present experiments show that a viewpoint intermediate be- 

 tween these two is correct for Pieris, and that while the antennae constitute a 

 very important, probably the most important, olfactory region of the body, they 

 do not constitute the sole olfactory region. 



Regardless of the results obtained by testing insects with mutilated 

 antennae, it has never seemed reasonable to the writer to suppose 

 that odorous air can pass quickly through the hard and dry chitin 

 covering the antennal organs. If it can, why not grant the same 

 privilege to all sense organs covered with thin chitin, including all 

 kinds of sense hairs and even the olfactory pores whose sense fibers, 

 according to other authors, are separated from the outside air by a 

 thin layer of chitin? In the higher animals the olfactory organs 

 (fig. 12) are separated from the outside air by only a thin watery 

 layer of mucus, and the latest results show that the free ends of the 

 olfactory cilia actually come in contact with the air. Eidmann (18) 

 erroneously supposed that the chitinous intima of insect intestines is 

 similar to the coverings of the so-called olfactory and taste organs of 

 insects. He proved chemically that aqueous solutions can pass slowly 



