1914.] NATURAL SCIENCES OF PHILADELPHIA. 327 



tained that the relative sizes of a few of the specimens were less 

 than 1.00, while most of them were greater than 1.00. 



A study of the anatomy of the pores shows that the diameters 

 of the peripheral sense fibers are proportional to the diameters of 

 the flasks. Of course, the greater the diameters of the peripheral 

 sense fibers, the more cytoplasm is exposed to the external air. The 

 diameters of the ends of the sense fibers cannot be measured, but 

 the diameters of the flasks can be accurately measured. To facilitate 

 matters, the largest pore on the femur of the leg measured and the 

 largest one on the front wing of each individual insect were drawTi 

 with the aid of a camera lucida. Figures 43 to 79 represent these 

 pores. The larger pore in each case is from the femur and the 

 smaller one is from the front ^ving. For our purpose each pore maj^ 

 be regarded as a circle having for its diameter the shorter diameter 

 of the pore as shown in the drawings. To obtain the relative sensi- 

 tiveness of all the pores on the legs of a given insect, the diameter 

 of the largest pore on the femur, the total number of pores on the 

 legs and the relative size of the given insect were used. To obtain 

 the relative sensitiveness of all the pores on the legs and wings 

 combined, the diameters of l^oth pores, the grand total number of 

 pores, and the relative size of the given insect were used. 



By this system of calculating it was determined that Cimhex with 

 its 1,216 pores smells 0.87 times as well as Microgaster which has 

 only 622 pores, and only 0.85 times as well as the smallest ant with 

 463 pores. In speaking of the relative sensitiveness obtained by 

 this system of calculating, a large probable error must always be 

 allowed and the figures only approximately represent the truth. 

 Allowing for the -probable error, all the winged individuals, except 

 three, placed between Cimhex and Ceropales in the table seem to 

 have the olfactory sense about equally developed. The three 

 exceptions are the ichneumon-fly (Megarhyssa), the female ant of 

 Aphcenogaster, and the male ant of Camponotus, all three of which 

 seem to smell slightly better than the others. The males of Campo- 

 notus probably smell slightly better than the females of the same 

 genus and considerably better than the winged forms of Formica. 

 The small workers of Camponotus seem to smell slightly better than 

 their large sisters and considerably better than the large workers 

 of Formica and of C. mela. According to the reaction times obtained 

 in determining the relative sensitiveness to odors of ants, the males 

 of Camponotus receive odor stimuli considerably better than the 

 workers and females of the same genus, but about as well as do the 



