No. 2.] PROTECTIVE RESEMBLANCES IN SPIDERS. 83 



through advantageous variation, but which we are unaljle to 

 explain, is Eriauchenus workmanni (fig. 6). 



Epeira prompta (a variety of parvula, Plate lY, fig. 2) is a 

 common spider in Wisconsin. It is most frequentlj'^ seen on 

 cedar bushes, where its color harmonizes with 

 that of the foliage and fruit. During the day 

 it usually rests on a branch near its web. Tlie 

 back of the abdomen is of a peculiar bluish 

 green, exactly like that of the lichens growni^ 

 on tree trunks. The bluish color is broken by ' 

 waving black lines which imitate the curling camtad^S '*'^°'" 

 edges of the lichens. The one represented 

 in the plate was found on an old cedar which was covered 

 with lichens. It was kept for two weeks in a glass-covered 

 box, where it spent most of the time crouching in a corner. 

 It built no web, but spun some irregular lines to run about 

 on. It ate gnats, flies, and once a little jumping spider, S. 

 pulex, which we were keeping in the same box, leaping upon 

 its prey, as noted by Hentz,* like an Attus. This seems a 

 curious habit to be acquired by an Epeirid, since these spiders, 

 as we have noticed among our captives, are usually dependent 

 for food upon what is caught in their webs. Prompta moves 

 awkwardly, but very rapidly. 



Drapetisca socialis, while quite a different looking spider, is 

 protected in the same way — by its resemblance to tlie bark 

 upon which it lives. Emerton speaks of finding it on the bark of 

 spruce trees, which it " closely resembles in color."! Menge says 

 that it is common in Prussia, where it is seen in great numbers 

 on fir trees, whose spotted bark it resembles in color, so that it 

 is not easily seen.J We have found them, most commonly, 

 upon birch trees, and in this situation their color adaptation 

 is perfect. Both the spider and the peeling bark of the tree are 

 of a light silvery brown, covered with little blackish marks. 



* "This very distinct species is very active after sunset, running with great 

 speed, and leaping like an ^li(((s. It is motionless during the day." Loc. cit., p. 112. 

 + New England Therididce, p. 67. 

 ; Pfeussische Spinnen, p, 142. 



