TARSAL CHEMORECEPTORS OF BUTTERFLIES 197 



the number of responses obtained from a group of animals con- 

 sidered collectively, is, 1 M saccharose > distilled water > 1 M 

 hydrochloric acid > M/600 quinine sulphate > 1 M sodium 

 chloride. 



The effectiveness of pure water in stimulating the tarsi in 

 butterflies is of particular interest in connection with the habit 

 of many species to gather in moist places and suck up water. 

 The cloud of butterflies about the drying mud puddle in summer 

 is familiar enough. Tutt ('97) has collected a number of exceed- 

 ingly interesting observations on the drinking habits of butter- 

 flies and moths. Sometimes the amount of water consumed by 

 these animals is almost inconceivable. Thus, Tutt ('97, p. 

 77-78) quotes Baron as follows : 



One morning, whilst sitting by the side of one of these streams, I 

 noticed the Papilio, which is an insect measuring four inches across the 

 wings, resting on a wet bank, and, wishing to procure it as a specimen, 

 I approached it as gently as possible, the creature being apparently so 

 absorbed in what it was about as to be totally unconscious of my prox- 

 imity to it. Noticing strange and unaccountable movements — sundry 

 jerks and probings with its proboscis — I quietly sat down near it, in 

 order to watch it more closely. I observed that every second or two 

 a drop of pure liquid was squirted (not exuded merely) from the tip of 

 its abdomen. I picked up a leaf that was lying near, and inserted the 

 edge of it between the insect's body and ihe ground, so as to catch the 

 liquid. Unfortunately I had no watch with me at the time nor means 

 of measuring liquids, but I reckoned that about thirty drops were 

 emitted per minute. I held the leaf for about five minutes, as nearly 

 as I could reckon, and at the end of that time there was caught in it 

 about a saltspoon of what seemed to be pure water, without either 

 taste or color. After watching the butterfly for a time I seized it by 

 the wings between my thumb and fingers with the greatest ease, so 

 utterly lost did it appear to be to what was going on near it. In another 

 spot I saw as many as sixteen of these large butterflies within the space 

 of a square foot, all engaged in the same strange action. Some of them 

 emitted the liquid more frequently than others; and one of them 

 squirted the liquid so as to drop fully a third of an inch beyond the 

 point on the ground perpendicular with the end of its body. It was 

 at this spot that I saw the second species of butterfly alluded to, Appias 

 saha, also engaged in the same curious proceeding. 



Of course, caution is necessary in interpreting observations 

 such as the above, for dissolved substances in the water undoubt- 

 edly play a considerable role. The responsiveness to water, 



