470 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1920. 



shown that the seat is not located in the spiracles or breathing pores 

 on the sides of the insect's body. With the spiracles eliminated there 

 remained only the view that the seat of smell must be in the antennae 

 or feelers. (Fig. 4, a.) This view was still more or less doubted up 

 to 1880, when Hauser's comprehensive and apparently infallible 

 results appeared in print. His results were generally accepted, and 

 for several years the debated question was settled, but a critical analy- 

 sis of his results has proven to the satisfaction of the present writer 

 that the antenna 1 view can not hold good either from an experimental 

 or from an anatomical viewpoint. 



In 1909 the present writer began to study the senses in spiders. 

 After a period of two years he described and determined the func- 

 tion of the lyriform (lyre-shaped) organs in spiders, and in 1911 

 began to work on similar organs, then called Hicks's vesicles but now 

 olfactory pores, common to insects. Up to date he lias thoroughly 

 studied the olfactory pores in many families of spiders and in most 

 of the insect orders, including dozens of families and hundreds of 

 species. So far he has never failed to find these organs in any speci- 

 men examined, and furthermore they are probably present in all 

 larval forms, although the larvae of only two orders have yet been 

 examined. As in spiders, they are widely scattered over the body, 

 head, and appendages of insects, but the more highly developed the 

 insect the more they are arranged in groups, most of the groups 

 being found on the legs, wings, and mouth parts. So far only a few 

 olfactory pores have been found on the antennae, these being pres- 

 ent on the bases of the antennae of bees, grasshoppers, roaches, and 

 crickets. 



Briefly described, an olfactory pore is nothing more than a nerve 

 (fig. 6, N) passing through a tiny hole in the " skin " or chitin (Ch) 

 of the insect. The internal and external anatomy varies considerably, 

 according to the insect order examined, but structurally those on the 

 halteres (rudimentary hind wings of flies and mosquitoes) have 

 reached the highest degree of perfection. Here they are beautifully 

 sculptured and their architecture is really marvelous, as may be seen 

 by looking at figures 7 and 8, and furthermore since they stand, knob- 

 like, above the " skin " they are well protected by large curved hairs 

 (figs. 7 and 8, Hr) bending over them. 



In the experimental part of the work, the writer used hundreds of 

 ants, bees, hornets, beetles, grasshoppers, crickets, and caterpillars. 

 The insects were first tested to ascertain their normal reaction times 

 to various sources of odors, among which were their food and some 

 others not regarded as irritants. Some of the adult insects were then 

 mutilated by having their antennae either cut off or covered with a 

 harmless substance, while the other adults were nrutilated by having 

 most of their olfactory pores either covered with a harmless sub- 



