88 ON THE HABITS OF ANTS. [LECT. 



Professor Tyndall, who was good enough to look at them 

 with me, like microscopic stethoscopes. 



The organs of vision are in most ants very complex 

 and conspicuous. There are generally three ocelli 

 arranged in a triangle on the top of their heads, and 

 on each side a large compound eye. 



The mode in which the eyes act is by no means under- 

 stood. They consist of a number of facets, varying 

 from 1 5 ; in Ponera contracta, to more than 1,000 in 

 each eye as, for instance, in the males of F. pratensis. 

 In fact these, so far fortunate, insects realize the wish of 

 the poet : 



" Thou lookest on the stars, my love ; 



Oh would that I could be 

 Yon starry skies with thousand eyes 

 That I might look on thee." 



But if the male of F. pratensis sees 1,000 images 

 of the queen at once, this would seem to be a bewil- 

 dering privilege, and the prevailing opinion among 

 entomologists is that each facet only takes in a portion 

 of the field of view. 



However this may be, the sight of ants does not seem 

 to be very good. In order to test how far they are guided 

 by vision, I made the following experiments. I placed 

 a common lead-pencil on a board, fastening it upright, 

 so as to serve as a landmark. At the base I placed 

 a glass containing food, and put a L. niger to the 

 food ; when she knew her way from the glass to the nest 

 and back again perfectly well, she went quite straight 

 backwards and forwards. I then took an opportunity 

 when the ant was on the glass, and moved the glass 

 with the ant on it about three inches. Now, under 



