DRINKING HABITS AND WATER LIFE. 23 



IV. 



An interesting note upon the feeding lialiits of spiders has been com- 

 municated to me by the Philadelphia entomologist, Mr. P. P. Calvert. While 

 studying the habits of dragonflies he observed early in May a 

 species of spider, which appears to be a young Dolomedes sex- 

 punctatus, feeding upon newly transformed imagines of these 

 insects. The spiders were lurking upon tall grasses and water plants, on 

 the margin of a small pool near Bartram's Garden in Philadelphia. The 

 dragonflies had come to these plants to transform, and before their wings 

 were dried and ready for flight, while they were yet helpless, the young 

 Dolomedes seized them and sucked their juices. The two species which 

 were thus preyed upon are Ischnura vcrticalis Say and Nehalannia posita. 

 Ilagen, both of them small species. Dolomedes, as heretofore 

 described (see Index of Vol. II.), is a semiaquatic species, running 

 rapidly upon the water to seize insects, and remaining for a con- 

 siderable length of time underneath the surface. The mother deposits her 

 cocoon in a large leafy nest among the bushes, within which the young 

 are hatched. The specimen shown me by Mr. Calvert as taken while in 

 feeding on dragonflies was not more than half grown. We thus have a 

 glimpse of one of the methods in which this Citigrade species, and doubt- 

 less many others, obtain food. It shows also the disadvantages and perils 

 of insects during transformation, when they are exhausted by the process 

 and have not acquired the natural facilities for escape or defense. 



V. 



Various spiders run fearlessly on the surface of the water ; some even 

 descend into it spontaneously, the time during which they can respire, 



when immersed, depending upon the quantity of air confined by 

 H , ., the surrounding liquid among the hairs with which they are 



clothed. Ip this manner the European Argyroneta aquatica is 

 able to pursue its prey, to construct its dome shaped dwelling, and to live 

 habitually in water. There are, however, a few exceptions of extremely 

 small spiders, Neriena longipalpis and Savignia frontata, for example, 

 which, though they do not enter water voluntarily, can support life in it 

 for many days, and that without the external supply of air so needful to 

 the existence of Argyroneta under similar circumstances. 1 This is certainly 

 a remarkable fact. I have known spiders that seemed to be drowned by 

 long immersion in waler to revive shortly after being taken out ; even those 

 plunged in alcohol, if not kept therein too long, will recover from seeming 

 death. But that these small and delicate creatures should live several days 

 in water surely strains one's belief in even so trustworthy an observer as 

 Black wall. 



1 Blackwall, Spiders Gt. B. & I., Introduction, page 9. 



