TARSAL SENSITIVITY IN PYRAMEIS 447 



was substituted for distilled water, and again the animals 

 generally revived. The diet of saccharose was continued for 

 three days, after which the animals were subjected to a second 

 period of total inanition, followed by a second period of water 

 diet, followed in turn by a second period of IM saccharose diet. 

 Those individuals which survived the entire experiment were 

 thus carried through six nutritional periods: a first period of 

 total inanition, a first period of water diet, a first period of IM 

 saccharose diet, a second period of total inanition, a second period 

 of water diet, and a second period of IM saccharose diet. 



The method employed in making trials was the following. 

 The animal was placed in a holder manipulated by hand, and 

 was held with its four ambulatory tarsi in contact with a flat 

 layer of absorbent cotton contained in a Syracuse watch-glass 

 and saturated with the stimulating substance. Each trial with 

 a given concentration of saccharose was immediately preceded 

 by a trial with distilled water alone. If there was any evidence 

 of response in the preliminary trial the saccharose test was 

 abandoned, thereby avoiding any possibility of misinterpretation. 

 No visible movement of the proboscis during one minute con- 

 stituted a no response, while extensions of the proboscis during 

 the same interval, whether partial or complete extensions, con- 

 stituted a response. After each trial with saccharose the feet 

 were carefully rinsed in distilled water and dried by contact with 

 clean filter-paper. 



Excepting the first three to five days after hatching and days 

 of responsiveness to water alone, an attempt was made to deter- 

 mine the threshold concentration of saccharose for each animal 

 daily. In general, this was accomplished by means of four 

 determinations, although occasionally as many as six or seven 

 were made. These determinations were made at least one hour 

 apart. Between them, however, tests with other substances, 

 viz., IM saccharose, 2M NaCl, and M/10 quinine hydrochloride, 

 were being made at minimal intervals of fifteen minutes. As 

 far as I was able to observe, the trials with these various sub- 

 stances in nowise affected the threshold of response to saccharose. 



