252 Annals Entomological Society of America [Vol. IX, 



head toward the south. A soft wind was blowing from that 

 direction, and a south wind in October may have been sufficient 

 stimulus to excite this choice of position. 



An inspection of the field on several other days yielded 

 the following data : 



October 7, at 5:30 p. m., 26 individuals of P. protodice were 

 asleep on three species of plants as follows : 



On the seed-mass of white snake-root 17 



On the white flowers of Aster multiflora 7 



On the white flowers of Melolalus alba 2 



The goldenrod in bloom in abundance near by bore none at 

 all. They all were fast asleep so they could be picked up and 

 replaced on the twig or even on my coat. Two of them clung 

 thus to my coat all the way to my home, a distance of two 

 blocks. These 26 insects rested horizontally on the top of the 

 flower with their heads in the following direction : 

 South, 15; East, 4; North, 3; West, 4. 



The direction of the wind could not be ascertained on this 

 evening; there was very little and it seemed to be variable. 



On October 14 at 5:40 p. m. the wind was directly from the 

 south. The butterflies were again at their old haunts and 

 asleep. Of the 34 examined this evening, 28 were resting 

 horizontally on the tops of the white snakeroot, and 3 just 

 below, in a vertical position head upward, and 3 were on the 

 goldenrod in a vertical position. And, it surely cannot be mere 

 coincidence again, every one of the 34 directly faced the south. 



In addition there were this evening three yellow butterflies, 

 Colias eurytheme and C. philodice, on the goldenrod and snakeroot. 

 Two were in the same position in relation to the wind as above, 

 and the one on the goldenrod was in a vertical position with the 

 ventral aspect of the body toward the wind. 



The next observations were at the same hour on October 17. 

 The temperature had fallen by this time, and a chill wind was 

 blowing from the southwest. There were only 14 butterflies 

 to be seen, 12 of them resting on the tufts of the snakeroot, and 

 2 -on melolotus, but each and every one of these insects was- 

 facing the south. 



By October 18 a more pronounced drop in temperature had 

 occurred. A careful search revealed only one butterfly. The 

 wind was from the southeast, and this numbed insect was 



