QO ENTOMOLOGY 



organs are not only structurally adapted for the reception of olfactory 

 stimuli, but their numerical differences accord with the observed differ- 

 ences in the olfactory powers of the two sexes, there being no other 

 antennal end-organs to enter into the consideration. 



Dr. N. E. Mclndoo has denied that the antennae are olfactory 

 organs. He finds, in all the large orders of insects, and on almost all 

 parts of the body and legs, on the bases of the wings, and in other situa- 

 tions, the structures that he terms olfactory pores, to which he has 

 devoted an immense amount of study. 



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

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



sc- 



..-h 



FIG. 136. Longitudinal section of a por- FIG. 137. Longitudinal section of apex 



tion of a caudal appendage of a cricket, of palpus of Pieris. c, cuticula; h, hypo- 



Gryllus domesticus. b, bladderlike hair; c, dermis; n, nerve; s, scales ;sc, sense cells. 



cuticula; h, hypodermis; n, nerve; ns, non- After VOM RATH. 

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

 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 antennae rapidly as they near her. The female, mean- 

 while, exhales an appreciable odor, chiefly from the region of the ovi- 

 positor, 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 

 antennae, however, he flutters about in an aimless way and is no longer 

 able to find the female. 



Among beetles, males of Polyphylla gather and scratch at places 



