368 SIR J. LUBBOCK ON ANTS, BEES, AND WASPS. 



into the extreme end beyond the violet. At 7 they followed the 

 line of the red at one end, coming about | inch within it, 

 which was not owing to want of room, as one side of the nest 

 was almost unoccupied; at the other end they were all carried 

 3 inches beyond the end of the violet. 



I then arranged the same ants in a wooden frame con- 

 sisting of a base and two side walls, between which in the 

 middle was a perpendicular sliding door. The pupae had been 

 arranged by the ants in the centre of the nest, so that some were 

 on each side of the door. We then, by means of a strong induc- 

 tion-coil, threw a magnesium-spark on the nest from one side, 

 and the light from a sodium-flame in a Bunsen burner on the 

 other, the light being in each case stopped by the door, which was 

 pressed close down on the nest. In this way the first half was 

 illuminated by the one light, the second by the other, the appa- 

 ratus being so arranged that the lights were equal to our eyes — 

 that, however, given by the magnesium, consisting mainly of blue, 

 violet, and ultra-violet rays, that of the sodium being very yellow and 

 poor in chemical rays. In a quarter of an hour the pupae were all 

 carried into the yellow. The sodium light being the hotter of the 

 two, to eliminate the action of heat I introduced a water-cell 

 between the ants and the sodium-flame, and made the two sides as 

 nearly as possible equally light to my eye. The pupae, however, 

 were again carried into the sodium side. 



I repeated the same experiment as before, getting the magne- 

 sium-spark and the sodium-flame to the same degree of intensity, 

 as nearly as my eye could judge, and interposing a water-screen 

 between the sodium-flame and the ants. The temperature was 

 tested by the thermometer; but I could distinguish no differ- 

 ence between the two sides. Still the ants preferred the sodium 

 side. This I repeated twice. I then removed the magnesium- 

 spark somewhat, so that the illumination on that side was very 

 much fainter than on the other ; still the pupae were carried 

 into the sodium-light. I then turned the nest round so as to 

 bring them back into the magnesium. They were again carried 

 to the sodium side. 



Once more I repeated the same experiment. The light on the 

 magnesium side was so faint that I could scarcely see the pupae, 

 those on the sodium side being quite plain. The thermometer 

 showed no difference between the two sides. The pupae were 

 carried into the sodium-light. I then turned the nest round 



