228 PRINCIPLES AND CONCLUSIONS. 



female beetles or butterflies that mated freely when normal did so only 

 occasionally after the antennae were lost. 



Olfactory pores. — Hicks (1857-1860) was the first to discover the pores 

 now termed olfactory by Mclndoo, who summarizes the former's results 

 as follows (1914 2 :38). 



"To summarize Hicks's three papers, he discovered these pores on the halteres and 

 on the bases of the wings of all Diptera examined; on the bases of all four wings 

 of the four- winged tribes; on the trochanter and femur of all insects, and occasionally 

 on the tibia. He examined many species representing various insect orders and found 

 the pores even on the lower insects, such as the earwig. In such wingless insects as 

 the worker and soldier ants, he infers that these pores are much more abundant on 

 the legs than they are on these appendages in the winged insects. Hicks suggested 

 an olfactory function for all of these pores, whether on the wings or legs, but he per- 

 formed no experiments of any kind. In regard to smell in insects and the function 

 of the pores on the legs, he says: 'The delicacy with which odors are perceived by 

 many insects argues an olfactory apparatus of considerable perfection; and it seems 

 to me not impossible that these latter-named organs (those on the legs) may be in 

 some way connected with the sense of smell, or perhaps with some sense not to be 

 found in the Vertebrata.'" 



Mclndoo mentions the work of about a dozen other investigators on 

 these pores, two of whom regarded them as olfactory in function. 



Mclndoo's own studies (1914) of the pores are much the most detailed 

 and comprehensive, and his experiments upon their function appear to 

 be the most extensive in the entire field of olfaction. The Hicks vesicles 

 or olfactory pores consist of inverted flasks in the chitin and of fusiform 

 sense-cells lying beneath the mouths of the flasks. The sense fiber pierces 

 the bottom of the cone and enters the pore aperture, thus coming in direct 

 contact with the air containing odorous particles, contrary to the condition 

 in the antennae, where the odors must pass through a hard membrane 

 in order to stimulate the sense-cells. In the case of the honey-bee the pores 

 are found on the bases of the wings, on the legs, and on the sting of worker 

 and queen. They also occur on the mouth-parts of all Hymenoptera, while 

 they are lacking on the antennae of the honey-bee and probably all other 

 Hymenoptera. For the legs of ants the number varies from 211 to 356 

 and for the winged ants the total number varies from 463 to 1,090. In the 

 honey-bee the queen has an average of 1,860, the worker 2,268, and the 

 drone 2,604; the averages for all four wings are 1,310, 1,510, and 1,998, 

 and for all six legs, 450, 658, and 606 respectively, the sting having an average 

 of 100. The total number for a bumble-bee was 1,627 and for a wasp 1,957; 

 the number of isolated pores is approximately one-half the number in groups, 

 except in the worker honey-bee, where it is somewhat less. 



Experiments with antennae removed, mutilated, or coated. — 



Mclndoo (1914 : 291) finds that worker bees with the left antennae 

 pulled off at the base reacted to the three essential oils, peppermint, thyme, 

 and wintergreen, in an average of 4.6 seconds in contrast to 2.3 seconds for 

 intact individuals. When 2 to 8 joints of the other antennae were removed, 

 the reaction-time rose proportionately from 15 seconds for the first case and 

 88 for the last. Bees with both antennae pulled off or covered with celloidin 

 failed entirely to respond to these oils. Drones with 4 or 5 joints of one 



