184 DWIGHT E. MINNICH 



A comparison of the results obtained in positions 1 and 2 

 shows that the butterflies actually responded less frequently in 

 the latter than they did in the former. This comparatively small 

 number of responses in position 2 must not be construed to mean 

 that distilled water is without effect on the tarsi. As we shall 

 see presently, such is not the case. It does show, however, 

 when compared with results obtained in position 3, that distilled 

 water is a vastly less effective stimulus for the tarsal chemo- 

 receptors than is applejuice. The difference in the results 

 obtained in positions 2 and 3, furthermore, demonstrates con- 

 clusively that the sense organs concerned are chemical and not 

 tactile, for distilled water and applejuice would be indistinguish- 

 able to tangoreceptors. 



In all three positions on the apparatus animals were some- 

 times observed to bend the antennae down to the substrate. 

 Since pan a, or pan b was always directly beneath these organs, 

 they were thus brought very close to, or into actual contact with, 

 the cloth saturated with applejuice or with distilled water. 

 There has been much evidence to show that the antennae con- 

 tain olfactory organs (distance chemoreceptors) . It might be 

 argued, therefore, that in spite of the fairly uniform distribution 

 of volatile materials over the apparatus, the ability of the animal 

 to bring its antennae in contact with the substrates in pan a 

 and pan b might assist materially in enabling it to distinguish 

 between them. The marked difference between the number of 

 responses in position 2 and that in position 3 might thus be at- 

 tributed, at least in part, to sense organs on the antennae. 



In order to test out the above possibility, I decided to remove 

 the antennae and repeat the experiments. The experiments 

 detailed in table 1 were carried out in forenoons. At the close 

 of these experiments, the antennae of all butterflies were ampu- 

 tated. The labial palps and the rudimentary fore legs were 

 likewise removed, for it seemed possible that these appendages 

 might also possess olfactory organs. After an hour for recovery, 

 the animals were subjected to the same number of trials as 

 previously. One specimen became moribund during the last 

 set of trials and had to be discarded. The total number of 

 trials in each position was thus 23, instead of 24 as in table 1. 



