THE SEX'S ATI OX S OF ANTS. 517 



greater the number of ommatidia and the more convex the surface of 

 the eye, it is very probable that only ants with well developed eyes, 

 like Formica , Pseudomyrma, etc., can distinguish objects by means of 

 these organs. Wasmann's experiments (1899^7) indicate that workers 

 of various species of Formica can see resting objects as large as a finger 

 at a distance of 5-10 cm., but that they are unable to see small objects, 

 like beetles, at a greater distance than 4-5 mm. My'own observations 

 tend to confirm these statements. Moving objects are, of course, much 

 more readily perceived. Indirect evidence of visual discrimination in 

 ants is furnished by the mimetic coloration and form of certain myrme- 

 cophiles (see Chapters XXI and XXII). Undoubtedly male ants, 

 which always have very large, convex eyes, are able to see the flying 

 females at a considerable distance. The function of the ocelli, so 

 highly developed in the males and females, has not been determined. 

 It has been suggested that they may be of use in seeing objects at very 

 close range and in dark places, like the galleries of the nest. 



On the whole, we are led to conclude that vision in worker and 

 female ants is very poorly developed, compared with the chemical and 

 mechanical senses (contact-odor and the perception of vibrations). 

 Indeed, ant behavior is so profoundly influenced by these senses, that 

 it may be said to differ fundamentally, not only from the behavior of 

 man and the higher mammals, but even from that of such closely allied 

 Hymenoptera as the bees and wasps. 



