TARSAL PERCEPTION 135 



repeated and the responses in the three positions were 4 per cent., 

 17 per cent., and 65 per cent, respectively. The responses with 

 Vanessa were in some respects less striking, but they were similar 

 in nature. In a further series of experiments it was shown that 

 Pyrameis, by means of its tarsi alone, is able to distinguish IM 

 saccharose solution from distilled water and such solutions as 

 IM HCl, M/600 quinine sulphate, and IM NaCl from either IM 

 saccharose or distilled water. Distilled water alone is a very 

 effective stimulus when applied to the tarsi. Minnich gives 

 reasons for concluding that chemoreceptors are located in all four 

 tarsi of the walking legs of Pyrameis, but gives no information 

 with respect to the structure and exact location of the sensillai 

 involved. Since perception takes place by means of actual 

 contact with the stimulus, he regards the organs involved as being 

 gustatory in function. 



In 1922 Minnich repeated his former tests and obtained very 

 similar results, and, according to the scheme adopted in this 

 second paper, the total responses of all the individuals tested 

 were 100 per cent, to IM saccharose, 84-7 per cent, to M/10 quinine 

 hydrochloride, and 51-6 per cent, to 2M NaCl. An intensive 

 study of the differences of response showed that Pyrameis could 

 differentiate between almost all, or probably all, these solutions. 



In a further series of experiments (Minnich, 1922a) it was 

 shown that contact of the four ambulatory tarsi with IM 

 saccharose solution will always effect an extension of the 

 proboscis, irrespective of the nutritional condition of the insect. 

 After a prolonged period of inanition with respect to saccharose 

 the tarsal sensitivity may be so delicate as to appreciate as low 

 as M/12,800, and may thus be as much as 256 times that of the 

 human tongue. This highly developed sensitivity is doubtlessly 

 correlated with the fact that sugars form the chief food constituent 

 in Pyrameis. 



Additional observations and experiments were carried out by 

 Minnich (1926) with regard to the responses of three species of 

 common Muscid flies (Phormia regina, P. terrce-novce and Lucilia 

 serricata). The results obtained were very similar to those 

 derived from the experiments with Nymphalid butterflies. When 



