ANATOMY AND PHYSIOLOGY 



8l 



the female by means of antennal organs of smell, he finds that the male- 

 has on each antenna about 600 sensilla cceloconica and the female only 

 75; similarly in the geometrid Fidonia, in which the ratio is 350 to 100. 

 The sensilla styloconica, also, of these two genera are regarded as olfac- 

 tory organs. These two kinds of end-organs are not only structurally 

 adapted for the reception of olfactory stimuli, but their numerical dif- 

 ferences accord with the observed differences in the olfactory powers of 

 the two sexes, there being no other antennal end-organs to enter into the 

 consideration. 



Assembling. It is a fact, well known to entomologists, that the 

 females of many moths and some beetles are able by exhaling an odor to 



sc 



FIG. 134. Longitudinal section of a por- 

 tion of a caudal appendage of a cricket, 

 Gryllus domesticus. b, bladderlike hair; c, 

 cuticula; It, hypodermis; n, nerve; ns, non- 

 sensory setae; sc, sense cell; sh, sensory hair. 

 After VOM RATH. 



n 



FIG. 135. Longitudinal section of apex 

 of palpus of Pier is. c, cuticula; //, hypo- 

 dermis; n, nerve; s, scales; sc, sense cells. 

 After VOM RATH. 



attract the opposite sex, often in considerable numbers. Under favor- 

 able conditions, a freshly emerged^female of the promethea moth, exposed 

 out of doors in the latter part of the afternoon, will attract scores of the 

 males. A breeze is essential and the males come up against the wind ; 

 if they pass the female, they turn back and try again until she is located, 

 vibrating the antennas rapidly as they near her. The female, meanwhile, 

 exhales an appreciable odor, chiefly from the region of the ovipositor, and 

 males will congregate on the ground at a spot where a female has been. 

 If one of these males is deprived of the use of his antenna?, however, 

 7 



