THE SENSES AND THEIR ORGANS. 295 



V. 



The vision of spiders is evidently limited in extent, although it remains 



to be determined what that extent may be. Prof. Auguste Forel, so 



widely known for his distinguished studies of ants, records in a 



v ^ n ? 1 e paper on the " Senses of Insects," that if a cocoon be removed 



from a ground spider (Lycosa) to the distance of two or three 



inches, she will hunt about for it and have great difficulty in finding it. 



He states, moreover, that jumping spiders (Saltigrades) cannot perceive 



their prey at a distance greater than two or three inches. 1 



Professor Peckham, as the result of his experiments, concludes that 

 spiders, at least the Lycosids, even when they see their cocoons, are not 

 able to recognize them except through the medium of the sense of touch. 2 



But, on the other hand, the Peckhams' observations make it plain that 

 Saltigrades can see objects at a distance of at least ten inches. They fre- 

 quently saw them stalk their prey at a distance of five inches. They re- 

 peatedly held Astia vittata on one finger and allowed it to jump to a 

 finger of the other hand, gradually increasing the distance up to eight 

 inches. As the distance increased, the spider paused a longer time before 

 springing, gathering its legs together to make a good "ready." 



I have repeatedly verified this experiment with an adult female of 

 Phidippus morsitans. Holding the spider upon a box in which she had 

 been taken, I approached a finger within an inch of her face, until her 

 attention was evidently attracted. Presently she leaped the space, alight- 

 ing upon the 'finger. I then restored her to her position upon the box, 

 and by manipulation again tempted her to escape by vaulting twice the 

 distance. By gradually increasing the space, she finally jumped a distance 

 of from three and a half to four inches. Her whole action showed that 

 she had seen the object before her, had discerned the fact of an interven- 

 ing space, had carefully measured the distance, and then vaulted, success- 

 fully reaching the object. As usual on such occasions, she always kept 

 herself secure by a dragline attachment to the box from which she jumped. 



Twice the Peckhams saw a male Astia vittata chasing a female upon 



a table covered with jars, bags, and boxes. The female would leap rapidly 



from one object to another, or w r ould dart over the edge of a 



Good book or box so as to be out of sight. In this position she would 



O * r_ J_ ' 



s j,. remain quiet for a few moments, and then, creeping to the edge, 



grades. would peer over to see if the male were still pursuing her. If 

 he happened to be hidden, she would seem to go to him even 

 when ten or twelve inches away, and would quickly draw back. But in 

 case he was hidden behind some object, she would hurry off, seeming to 



1 Sensationes des Insectes, I. Recueil Zoologique Suisse, Tome IV., No. 1, pages 18, 19. 



2 Mental Powers of Spiders, pages 401, 402. 



