194 NATURE SKETCHES IX TEMPERATE AMERICA 



was inadvertently left on the table in a vase of water, about a 

 foot away from the nest of the spider. I left the room for about 

 half an hour at noon, never thinking of the spider. When I 

 returned I found that all three of the moths were missing, but 

 I soon found one of them on the table near the spider's nest, 

 with the spider complacently feasting on it, just as I have de- 

 picted her in the photographic illustration. The other two 

 moths, which had evidently been frightened by the spider, were 

 afterwards found unharmed in other parts of the room. That 

 there had been a struggle by the captive moth was shown by 

 the numerous moth scales strewn over the top of the table. 

 When it is remembered that the Datana moth is so much 

 larger than the spider, the fearlessniess of this spider is better 

 appreciated. 



In order to reach the moth the spider was obliged to crawl 

 up the side of a small glass vase containing water and the plants. 

 She then could easily jump on the stem and crawl out to the 

 leaves of the rasi)berry. Either the spider saw the nearest 

 moth from the table below, a distance of at least eight or nine 

 inches, or else she made a foraging trip on the plants without 

 first observing the moth from the table. In the latter case, 

 she accidentally discovered the moths after crawling out on 

 the leaves. 



In an interesting article by the Peckhams on "The Sense of 

 Sight in Spiders," they arrived at the conclusion, after experi- 

 ments on these Attids. that they see their insect prey when it 

 is motionless up to a distance of five inches; that they see insects 

 in motion at much greater distances; and that they see each 

 other distinctly up to at least twelve inches. It will be borne 

 in mind that the Datana moths I have referred to were quiet, 

 and it is much more probable that they were detected by the 

 spider from below the table top. 



Numerous species of these spiders frequent our fields and 

 forests. The part they play in the struggle for existence 

 among the insect life living in the same environment is but 

 little known. Yet, who can doubt that these fearless little 

 predaceous tigers are an important factor in the control of 

 insect life, and that they exert an influence on the population 

 of manv of these life forms. 



