206 AMERICAN SPIDERS 



bers wonderfully adapted for life near or on the water surface. 

 These amphibians are the handsome vagabonds of the family Pisau- 

 ridae, animals of large or even giant size that resemble the wolf 

 spiders closely in appearance but differ from them quite distinctly 

 in certain habits. The pisaurids broke away from the true wolves 

 early in their history, became committed to existence in moist areas, 

 and now seem largely limited in their distribution by the presence 

 of permanent streams or ponds. Often referred to as "water spi- 

 ders," they are however no more than cousins of the European 

 Argyroneta, a spider that has conquered the aquatic medium to 

 such an extent that it lays exclusive claim to that title. They are 

 also called "nursery web weavers" because of the spinning industry 

 of the females, but the most accurate appellation is that of "fisher 

 spider" a name that properly conveys their predaceous bent and 

 amphibious aptitude, as well as their occasional fondness for little 

 fishes. 



The typical fisher spider of the genus Dolomedes (Plate XXVI) 

 is a huge gray or brown spider with an oval abdomen and a longitu- 

 dinal cephalothorax more flattened than in the majority of the ly- 

 cosids. The integument exhibits many appressed plumose hairs, in 

 addition to various simple hairs and spines. The eyes have much 

 the same arrangement as in the Lycosidae, but the dorsal row of 

 four is not so strongly curved, and rarely is markedly larger than 

 the front row. This would seem to indicate that the range and 

 acuity of the fishers' eyes are less than those of the typical wolves. 

 They are big-eyed hunters, nevertheless, and seem to have excellent 

 day vision. 



No obvious physical features in the bodies of the Pisauridae 

 identify them as spiders of the water, but they walk over the sur- 

 face with a grace nearly equal to that of the water-striding insects. 

 The tarsal hairs are probably arranged to give buoyancy and to 

 push them when skating, but no conspicuous brushes or appendages 

 adorn their legs. Much of their success as pond skaters must be at- 

 tributed to their extreme lightness, which, repudiating their physical 

 bulk, keeps them from breaking through the surface film. Their 

 slight weight, however, while of great advantage on the surface, 

 becomes a liability when the situation calls for submarine action. 

 The aquatic pisaurids cannot swim as does Argyroneta, and seem 

 able to break the water surface only with great effort. Diving is 

 impossible unless they are able to exert considerable force with their 

 legs on some convenient support, and they remain submerged only 



