408 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 3 8 



rain spouts, etc. Webs have been observed in the prickly pear cactus, 

 where they spread about in the branches of the plant, with the central 

 nests in the trash on the ground. In the summer of 1934, perhaps 

 owing to the dryness, these spiders seem to have invaded the residential 

 districts in unusually large numbers, and one of us actually found a 

 mature black widow ensconced behind some books in the library. 

 Reports have come to us of their being found commonly in box cars 

 and a communication from fruit growers on the western slope of the 

 Colorado Rockies stated that grapes were going to waste because 

 pickers refused to work among the spider-infested vines. We have 

 seen the black widow or had reports of her in all parts of Colorado. 

 One was collected at an altitude of 8,000 feet near Buffalo Park, the 

 record altitude so far as our personal experience goes, and we collected 

 specimens both in 1934 and 1935 at an altitude of about 7,300 feet in 

 Estes Park. Recently we have received from a trustworthy source a 

 record of one taken near the village of Estes Park at an altitude of 

 8,200 feet. 



It is evident from the above statements that the spider recognizes 

 few geographic barriers except extreme cold and is also easily satisfied 

 with her local surroundings. At the same time, we have found 

 certain particular locations very densely populated and it would 

 appear that these are the most favorable in insuring survival. As 

 stated, we have collected approximately 6,500 spiders. By far the 

 greatest number of these were captured in the foothills country between 

 Denver and Colorado Springs. The hillsides are of disintegrating 

 limestone, forming fissures and clefts in the cliff faces, and with many 

 boulders on the gentler slopes. On the south slopes of these hills and 

 canyons, nearly every cleft and hole in the cliff has a web across its 

 mouth, nearly every boulder a web along its lower margin. The insect 

 life is not particularly abundant, but in such regions as this one can 

 collect several hundred spiders within a few hours. It should be 

 noted, however, that the size of the spider seems to be in direct 

 proportion to the size of the rock, and to collect large specimens one 

 must have the fortitude to turn over large rocks 



The web serves as a snare for the prey on which the spider feeds — 

 flies, beetles, grasshoppers, and the other insects that blunder into it. 

 We have even observed a small mouse entangled and several times 

 have seen the large western cicada, which is nearly as big as a mouse, a 

 victim. Usually whatever touches the web is securely caught almost 

 at the first contact, and its struggles only tie it the more tightly. 

 Large grasshoppers, however, can kick themselves free and require 

 prompt and energetic measures on the part of the spider. She 

 belongs to the family of "comb-footed" spiders which are distinguished 

 by the presence on the tarsus of the fourth pair of legs of a distinct 

 comb, consisting of a row of strong, curved, and toothed setae. The 



