TARSAL CHEMORECEPTORS OF BUTTERFLIES 175 



By means of the proboscis response, it has been possible -to 

 study both classes of chemoreceptors in Pyrameis and Vanessa 

 in a most satisfactory way. In the present paper, however, we 

 shall confine our attention to certain of the organs of contact 

 reception. These organs are apparently of considerable impor- 

 tance, and yet, as far as I am able to ascertain, they have com- 

 pletely escaped observation heretofore. Their morphology and 

 their general occurrence among insects are now being investi- 

 gated and will be reported upon subsequently. 



LITERATURE 



The organs of chemical sense in insects have been the subject 

 of a voluminous literature. Most of this work, however, has 

 been confined to the organs of olfaction, distance chemoreceptors, 

 while the organs of taste, contact chemoreceptors, have received 

 relatively little attention. 



Investigators have differed widely as to the exact location of 

 the olfactory organs. In connection with the data to be pre- 

 sented later, it is interesting to note that certain organs located 

 in part on the leg have been thought by some to function as 

 olfactory organs. Attention was first directed to these organs 

 by Hicks ('60). Recently Mclndoo ('14 a, '14 b, '14 c, 15, 17) 

 has made a very comprehensive study of the same organs in a 

 number of different groups of insects and is strongly convinced 

 that they are olfactory in function. Concerning the exact 

 location of these organs in Lepidoptera, he says ('17, pp. 40-41) : 



The disposition of the pores on the trochanters and femurs of a few 

 of the species is similar to that of the honey bee, but only occasionally 

 are pores found on the proximal ends of the tibiae and never on the 

 tarsi, as observed in the Hymenoptera. A few pores, iisuallj^ near the 

 distal ends of the tibiae, were seen in 21 of these specimens . . . . , 

 and pores were observed in the tibial spines of 12 individuals 



Among the butterflies studied was Vanessa antiopa, but in this 

 form Mclndoo found no pores distal to the proximal end of the 

 femur, where isolated pores occurred. As will be shown later, 

 this is a very different location from that occupied by the organs 

 we are to discuss. There is thus no possibility that the organs 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 33, NO. 1 



