NO. TO TROPISMS OF LEPIDOPTERA McINDOO 37 



with the four feet of the middle and hind legs touching the wire 

 screen and with the antennae extending directly over the cheesecloth 

 wet with apple juice. Since the front legs are rudimentary and not 

 used for walking, they were not considered in these tests. If the insect 

 responded at all in this position, the response was a truly olfactory one. 

 The hutterfly was next held in position 2 ; that is, with the head 

 and antennae just ahove the cheesecloth wet with distilled water and 

 with the feet of the middle legs resting on this wet cloth. If the insect 

 responded at all in this position, the response was either an olfactory 

 one or one hrought about by contact with the feet on the cloth, or the 

 response was a combination of both olfactory and contact stimuli. 

 The butterfly was finally held in position j ; that is, exactly like posi- 

 tion 2 except over the cheesecloth wet with apple juice. In this position 

 the insect always responded, and the responses were of the same kind 

 but differed in degree from those in position 2. As an average for 

 all the responses obtained in the three positions, position i gave 29 

 per cent ; position 2, ij per cent ; and position j, 100 per cent ; clearly 

 showing that these butterflies can distinguish apple juice from distilled 

 water merely by bringing their feet in contact with these liquids. 



In other series of tests Minnich used solutions of common sugar, 

 table salt, hydrochloric acid, quinine, and distilled water. In order 

 to compare closely the results obtained, the first four substances were 

 used on the basis of their molecular weights. Butterflies were able, 

 by means of their feet alone, to distinguish the sugar solution from 

 those of the hydrochloric acid and quinine, or from distilled water ; 

 and the salt solution from either sugar solution or distilled water. 



Now the question naturally arises : Are there special sense organs in 

 the tarsi of butterflies, which act as contact chemoreceptors ? Minnich 

 gives us definite information about their function, but leaves us in 

 the dark concerning their exact location and structure. Experimentally 

 he located them on the four tarsi of the middle and hind legs. Each 

 tarsus is five-jointed, the first joint being about as long as the other 

 four combined. Alinnich believes that these organs lie in the distal 

 end of the first joint, and particularly in the other four joints. He 

 further believes that they are not temperature organs, touch organs, 

 or organs to register the penetrating powers of liquids, but are chemi- 

 cal sense organs, perhaps somewhat similar to taste organs in man. 



Excepting tactile hairs, there are no other known sense organs in 

 the tarsi of butterflies, although no one apparently has looked for 

 other sense organs at this place. In 1917 the present writer (50) 

 reported finding olfactory pores on the legs of butterflies, but found 



