162 



under favorable environment, develop like behavior. Moreover, the query 

 arises, whether from some such accidental occasions, often repeated, may 

 not have sprung such a perfect navigating habit as that attributed to 

 Dolomedes fimbriatus, who makes for herself a raft of leaves united by 

 threads of silk, and so navigates the fens of Northumberland, England, in 

 search of prey. 



Like her congener Extensa, the Stilt spider has a wide distribution over 

 the United States. It is dispersed throughout the entire belt of 

 Eastern and Middle States ; and the collections of Dr. Marx locate 

 it in Empire City, Colorado ; Fort Bridger, Wyoming ; Kanayah, 

 Aleutian Isles ; Sitka, Alaska, and as far to the northeast as Unga Bay, Lab- 

 rador. 



III. 



The remarkably extended geographical distribution of these species of 

 Tetragnatha, and especially of T. extensa, necessarily raises the question as 

 to the effect of environment upon structure and habits. Through- 

 Distribu- ou ^ ^he wide area alluded to, the habits of Extensa, as far as I 

 p n> have been able to learn, are absolutely identical. I have studied 



and Habit t ne s pid er a ^ widely separated points in the United States, and 

 have made some observations of its habits in Great Britain. I 

 have also compared my observations with all recorded by European ob- 

 servers to which I could have access. There is no essential variation in the 

 testimony. The structure of the animal herself remains unchanged. The 

 character of her web is everywhere the same. Her cocooiiing habit, her 

 pairing habit, and in short all her life economy appear to be wholly unaf- 

 fected by change of climate, food, site, and elevation. It must be allowed, 

 indeed, that much remains to be done in the way of carefully noting the 

 habits of the species in the various localities at which it has been collected ; 

 but the spider has been known for more than a century, and, in Europe 

 particularly, has been studied by all arachnologists, and has had as much 

 attention given to her as to any other species, with the exception, perhaps, 

 of Epeira diademata. The above conclusion, therefore, may reasonably be 

 regarded as accurate. 



In this respect, Tetragnatha extensa is not alone. I have shown that 

 in the case of our large representatives of the genus Argiope (A. cophi- 

 naria and A. argyraspis) precisely the same facts obtain. (See 

 ._ er . Chapter VI.) From the rugged winters of New England to the 

 perpetual summer of Southern California, throughout the mount- 

 ain regions of Pennsylvania, and on the broad stretches of the Americm 

 plains, these spiders have been traced, and are found everywhere the same 

 in structure and habit. 



To these maybe added a large group of the genus Epeira, all of whirl) 

 are distributed over Europe, North America, portions of Asia, and probably 



